RESEARCH STARTER
World Trade Center bombing forensic investigation
The World Trade Center bombing forensic investigation refers to the extensive efforts undertaken to analyze and understand the events surrounding the tragic explosion that occurred on February 26, 1993. A powerful bomb detonated in the underground parking garage of the north tower, resulting in significant damage, including a massive hole and disruption of essential services in Lower Manhattan. The explosion prompted a swift response from various investigative agencies, including the FBI, who sifted through thousands of cubic yards of debris to gather evidence.
Key elements of the investigation involved tracing the rental van used for the bombing, which contained a substantial amount of explosive material. Forensic techniques such as chemical residue analysis and examination of physical evidence helped establish the van's central role in the blast. The investigation also revealed links to a broader conspiracy orchestrated by individuals affiliated with extremist groups, highlighting motivations rooted in political grievances.
Despite the extensive forensic work, the bombing underscored vulnerabilities in security at the Trade Center, prompting subsequent improvements. However, these changes would ultimately be tested again during the September 11 attacks, which saw the towers collapse as a result of coordinated terrorist actions. The investigation into the 1993 bombing serves as a crucial chapter in understanding the evolution of security measures and the challenges faced in preventing such attacks.
Authored By: Van Horne, Sheryl L. 1 of 3
Published In: 2020 2 of 3
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Full Article
DATE: February 26, 1993
THE EVENT: A car bomb exploded inside the parking garage below New York City’s World Trade Center’s north tower, killing six people and injuring more than one thousand. The explosion also disrupted public services and necessitated a massive cleanup effort.
SIGNIFICANCE: An intense forensic investigation by agents of the Federal Bureau of Investigation led to the arrest and conviction of four suspects. In the absence of eyewitnesses to the bombing, the convictions rested mostly on forensic evidence extricated from the blast’s rubble, telephone and bank records, and other documentary evidence. The bombing itself was regarded as an act of international terrorism that prompted changes in security measures in the United States.
At 12:17 P.M. on February 26, 1993, a huge bomb exploded in the underground parking garage below the north tower of New York City’s World Trade Center. Like its twin, the 110-story tower was part of a complex in which fifty thousand people worked on a typical day. The Trade Center complex also hosted as many as eighty thousand visitors a day.
The explosion blasted a crater approximately 150 feet wide that extended through four sublevels of concrete and ruptured sewer and water mains. The blast, which was felt several miles away, forced the evacuation of thousands of people from the building. It cut off telephone service to a large part of Lower Manhattan and ruptured nearby power lines. Without electrical power, many local radio and television stations could not broadcast for days after the blast.
In response to the chemical and biological hazards left in the wake of the blast, crews from the federal government’s Environmental Protection Agency led cleanup and containment efforts for debris and contaminated materials, while the Occupational Safety and Health Administration provided safety oversight for responders. The bomb itself had contained at least twelve hundred pounds of urea nitrate, a fertilizer that had been used only once in the explosions previously investigated by the Federal Bureau of Investigation (FBI) for about thirty years before the incident.
The Investigation
Four days after the blast, the New York Times received a letter from a group calling itself the Liberation Army Fifth Battalion, which claimed responsibility for the bombing. The group was unknown to law-enforcement agencies, but the FBI authenticated the letter as having come from a West Bank Palestinian named Nidal A. Ayyad. Its message called the bombing attack a response to the American support of Israel and American interference in Middle Eastern affairs. It also threatened further attacks if the US government failed to change its Middle Eastern policies, a warning that is still recalled in the annual commemorations that observe a moment of silence at 12:18 p.m., the time of the explosion.
Many government agencies responded to the bombing by sending investigation teams to the site, with the FBI serving as the lead agency and working with other partners, including the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and the New York City Police Department (NYPD). The early teams to arrive at the scene included FBI agents and specialists from the FBI’s explosives unit. During the seven days following the bombing, more than three hundred law enforcement officers sifted through the approximately 2,500 cubic feet of debris created by the blast. A bomb technician working for the federal ATF found the part of a nearly destroyed van with a vehicle identification number (VIN). That information made it possible to trace the van to the agency that had rented it and from there to the renter, another West Bank Palestinian named Mohammed A. Salameh.
Reconstructing the Crime
As law enforcement investigators worked to reconstruct what had happened, other evidence pointed to the rental van, later identified as a Ryder van, as the source of the blast within the building. In addition to finding chemical residues in the air, ATF agents discovered physical evidence of “feathering,” or stretching, of the van and dimpled metal near the van that had been liquefied by the heat of the blast and had shot out, leaving small indentations in nearby objects. This physical evidence indicated that the van itself was at the center of the blast.
Other forensic investigators collected detailed documentary and physical evidence that would lead to the apprehension of the primary suspects in the case. In 1991, a Kuwaiti-born national named Ramzi Yousef, who appeared to be the mastermind behind the bombing, apparently began planning the attack with his uncle, Khalid Sheikh Mohammed, a member of the radical Muslim group al-Qaeda who helped fund the conspiracy. Their goal was to cause one of the Trade Center’s towers to fall on the other, maximizing the damage. Police later found bomb-making instructions in the luggage of Yousef’s partner, Abdul Rahman Yasin, an American of Iraqi heritage who is still listed by the FBI as wanted in connection with the bombing.
The bomb contained a urea nitrate explosive device augmented with hydrogen gas cylinders intended to increase the destructive force of the blast. The conspirators had allegedly considered incorporating sodium cyanide to the mixture in the hope that cyanide gas would be disseminated throughout the building’s ventilation system.
After the attack, inquiries into how it occurred found that security in the World Trade Center garage had been seriously lacking, despite the fact that the Port Authority of New York and New Jersey had identified the parking areas and other access points as vulnerable to terrorist attack in 1985. Security in the World Trade Center was afterward greatly improved. The investigation into the 1993 bombing and the enhanced security measures initiated in its wake were rendered irrelevant on September 11, 2001, when hijackers crashed two planes into the twin towers of the World Trade Center, causing both towers to collapse. The forensic investigation into that tragedy lasted years, with DNA analysis of the remains of some of the 2,977 victims of the attacks ongoing in the 2020s.
Bibliography
Associated Press. “Bell Tolls as New York Marks the Anniversary of the 1993 World Trade Center Bombing.” AP News, 26 Feb. 2025, apnews.com/article/world-trade-center-bombing-anniversary-fb1c22d1d3fee523df733a53d0872351. Accessed 18 Feb. 2026.
Behar, Richard. “The Secret Life of Mahmud the Red.” Time, 4 Oct. 1993, pp. 54–61.
“The Bombing of the World Trade Center.” Federal Bureau of Investigation, 27 July 1993, www.911memorial.org/sites/default/files/inline-files/FBI%20Report%20on%20the%20Bombing%20of%20the%20World%20Trade%20Center%2C%2019930727_0.pdf. Accessed 18 Feb. 2026.
Caram, Peter. The 1993 World Trade Center Bombing: Foresight and Warning. Janus, 2001.
City of New York. “Mayor Adams, Chief Medical Examiner Dr. Graham Announce Three New Identifications of World Trade Center Victims.” NYC.gov: Office of Chief Medical Examiner, 7 Aug. 2025, www.nyc.gov/site/ocme/news/cm0325/mayor-adams-chief-medical-examiner-dr-graham-three-new-identifications-world-trade. Accessed 18 Feb. 2026.
Dwyer, Jim, et al. Two Seconds Under the World: Terror Comes to America—The Conspiracy Behind the World Trade Center Bombings. Crown, 1994.
Federal Bureau of Investigation. “World Trade Center Bombing 1993.” FBI.gov, U.S. Department of Justice, www.fbi.gov/history/famous-cases/world-trade-center-bombing-1993. Accessed 18 Feb. 2026.
History. “7 Facts about the 1993 World Trade Center Bombing.” HISTORY, 24 Aug. 2021, www.history.com/articles/world-trade-center-bombing-1993-facts. Accessed 18 Feb. 2026.
“Matter of World Trade Ctr. Bombing Litig.” New York State Law Reporting Bureau, 22 Sept. 2011, nycourts.gov/REPORTER/3dseries/2011/2011_06501.htm. Accessed 18 Feb. 2026.
“1993 World Trade Center Bombing Investigation.” National September 11 Memorial and Museum, 2023, www.911memorial.org/connect/blog/1993-world-trade-center-bombing-investigation. Accessed 16 Aug. 2024.
Pellowski, Michael J. The Terrorist Trial of the 1993 Bombing of the World Trade Center: A Headline Court Case. Enslow, 2003.
Pereira, Ivan. “Forensic Teams Look Back at 20-Year Mission to Identify World Trade Center Remains.” ABC News, 9 Sept. 2021, abcnews.go.com/US/forensic-teams-back-20-year-mission-identify-world/story?id=79899068. Accessed 16 Aug. 2024.
Reeve, Simon. The New Jackals: Ramzi Yousef, Osama Bin Laden, and the Future of Terrorism. Northeastern University Press, 1999.
Simon, Jeffrey D. The Terrorist Trap: America’s Experience with Terrorism. 2nd ed., Indiana University Press, 2001.
Weaver, Mary Anne. “The Trail of the Sheikh.” The New Yorker, 12 Apr. 1993, pp. 71–89.
Full Article
DATE: February 26, 1993
THE EVENT: A car bomb exploded inside the parking garage below New York City’s World Trade Center’s north tower, killing six people and injuring more than one thousand. The explosion also disrupted public services and necessitated a massive cleanup effort.
SIGNIFICANCE: An intense forensic investigation by agents of the Federal Bureau of Investigation led to the arrest and conviction of four suspects. In the absence of eyewitnesses to the bombing, the convictions rested mostly on forensic evidence extricated from the blast’s rubble, telephone and bank records, and other documentary evidence. The bombing itself was regarded as an act of international terrorism that prompted changes in security measures in the United States.
At 12:17 P.M. on February 26, 1993, a huge bomb exploded in the underground parking garage below the north tower of New York City’s World Trade Center. Like its twin, the 110-story tower was part of a complex in which fifty thousand people worked on a typical day. The Trade Center complex also hosted as many as eighty thousand visitors a day.
The explosion blasted a crater approximately 150 feet wide that extended through four sublevels of concrete and ruptured sewer and water mains. The blast, which was felt several miles away, forced the evacuation of thousands of people from the building. It cut off telephone service to a large part of Lower Manhattan and ruptured nearby power lines. Without electrical power, many local radio and television stations could not broadcast for days after the blast.
In response to the chemical and biological hazards left in the wake of the blast, crews from the federal government’s Environmental Protection Agency led cleanup and containment efforts for debris and contaminated materials, while the Occupational Safety and Health Administration provided safety oversight for responders. The bomb itself had contained at least twelve hundred pounds of urea nitrate, a fertilizer that had been used only once in the explosions previously investigated by the Federal Bureau of Investigation (FBI) for about thirty years before the incident.
The Investigation
Four days after the blast, the New York Times received a letter from a group calling itself the Liberation Army Fifth Battalion, which claimed responsibility for the bombing. The group was unknown to law-enforcement agencies, but the FBI authenticated the letter as having come from a West Bank Palestinian named Nidal A. Ayyad. Its message called the bombing attack a response to the American support of Israel and American interference in Middle Eastern affairs. It also threatened further attacks if the US government failed to change its Middle Eastern policies, a warning that is still recalled in the annual commemorations that observe a moment of silence at 12:18 p.m., the time of the explosion.
Many government agencies responded to the bombing by sending investigation teams to the site, with the FBI serving as the lead agency and working with other partners, including the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and the New York City Police Department (NYPD). The early teams to arrive at the scene included FBI agents and specialists from the FBI’s explosives unit. During the seven days following the bombing, more than three hundred law enforcement officers sifted through the approximately 2,500 cubic feet of debris created by the blast. A bomb technician working for the federal ATF found the part of a nearly destroyed van with a vehicle identification number (VIN). That information made it possible to trace the van to the agency that had rented it and from there to the renter, another West Bank Palestinian named Mohammed A. Salameh.
Reconstructing the Crime
As law enforcement investigators worked to reconstruct what had happened, other evidence pointed to the rental van, later identified as a Ryder van, as the source of the blast within the building. In addition to finding chemical residues in the air, ATF agents discovered physical evidence of “feathering,” or stretching, of the van and dimpled metal near the van that had been liquefied by the heat of the blast and had shot out, leaving small indentations in nearby objects. This physical evidence indicated that the van itself was at the center of the blast.
Other forensic investigators collected detailed documentary and physical evidence that would lead to the apprehension of the primary suspects in the case. In 1991, a Kuwaiti-born national named Ramzi Yousef, who appeared to be the mastermind behind the bombing, apparently began planning the attack with his uncle, Khalid Sheikh Mohammed, a member of the radical Muslim group al-Qaeda who helped fund the conspiracy. Their goal was to cause one of the Trade Center’s towers to fall on the other, maximizing the damage. Police later found bomb-making instructions in the luggage of Yousef’s partner, Abdul Rahman Yasin, an American of Iraqi heritage who is still listed by the FBI as wanted in connection with the bombing.
The bomb contained a urea nitrate explosive device augmented with hydrogen gas cylinders intended to increase the destructive force of the blast. The conspirators had allegedly considered incorporating sodium cyanide to the mixture in the hope that cyanide gas would be disseminated throughout the building’s ventilation system.
After the attack, inquiries into how it occurred found that security in the World Trade Center garage had been seriously lacking, despite the fact that the Port Authority of New York and New Jersey had identified the parking areas and other access points as vulnerable to terrorist attack in 1985. Security in the World Trade Center was afterward greatly improved. The investigation into the 1993 bombing and the enhanced security measures initiated in its wake were rendered irrelevant on September 11, 2001, when hijackers crashed two planes into the twin towers of the World Trade Center, causing both towers to collapse. The forensic investigation into that tragedy lasted years, with DNA analysis of the remains of some of the 2,977 victims of the attacks ongoing in the 2020s.
Bibliography
Associated Press. “Bell Tolls as New York Marks the Anniversary of the 1993 World Trade Center Bombing.” AP News, 26 Feb. 2025, apnews.com/article/world-trade-center-bombing-anniversary-fb1c22d1d3fee523df733a53d0872351. Accessed 18 Feb. 2026.
Behar, Richard. “The Secret Life of Mahmud the Red.” Time, 4 Oct. 1993, pp. 54–61.
“The Bombing of the World Trade Center.” Federal Bureau of Investigation, 27 July 1993, www.911memorial.org/sites/default/files/inline-files/FBI%20Report%20on%20the%20Bombing%20of%20the%20World%20Trade%20Center%2C%2019930727_0.pdf. Accessed 18 Feb. 2026.
Caram, Peter. The 1993 World Trade Center Bombing: Foresight and Warning. Janus, 2001.
City of New York. “Mayor Adams, Chief Medical Examiner Dr. Graham Announce Three New Identifications of World Trade Center Victims.” NYC.gov: Office of Chief Medical Examiner, 7 Aug. 2025, www.nyc.gov/site/ocme/news/cm0325/mayor-adams-chief-medical-examiner-dr-graham-three-new-identifications-world-trade. Accessed 18 Feb. 2026.
Dwyer, Jim, et al. Two Seconds Under the World: Terror Comes to America—The Conspiracy Behind the World Trade Center Bombings. Crown, 1994.
Federal Bureau of Investigation. “World Trade Center Bombing 1993.” FBI.gov, U.S. Department of Justice, www.fbi.gov/history/famous-cases/world-trade-center-bombing-1993. Accessed 18 Feb. 2026.
History. “7 Facts about the 1993 World Trade Center Bombing.” HISTORY, 24 Aug. 2021, www.history.com/articles/world-trade-center-bombing-1993-facts. Accessed 18 Feb. 2026.
“Matter of World Trade Ctr. Bombing Litig.” New York State Law Reporting Bureau, 22 Sept. 2011, nycourts.gov/REPORTER/3dseries/2011/2011_06501.htm. Accessed 18 Feb. 2026.
“1993 World Trade Center Bombing Investigation.” National September 11 Memorial and Museum, 2023, www.911memorial.org/connect/blog/1993-world-trade-center-bombing-investigation. Accessed 16 Aug. 2024.
Pellowski, Michael J. The Terrorist Trial of the 1993 Bombing of the World Trade Center: A Headline Court Case. Enslow, 2003.
Pereira, Ivan. “Forensic Teams Look Back at 20-Year Mission to Identify World Trade Center Remains.” ABC News, 9 Sept. 2021, abcnews.go.com/US/forensic-teams-back-20-year-mission-identify-world/story?id=79899068. Accessed 16 Aug. 2024.
Reeve, Simon. The New Jackals: Ramzi Yousef, Osama Bin Laden, and the Future of Terrorism. Northeastern University Press, 1999.
Simon, Jeffrey D. The Terrorist Trap: America’s Experience with Terrorism. 2nd ed., Indiana University Press, 2001.
Weaver, Mary Anne. “The Trail of the Sheikh.” The New Yorker, 12 Apr. 1993, pp. 71–89.