On February 26, 1993, at 12:18 p.m., a small cell of terrorists, with links to a local radical mosque and broader Islamist terror networks, detonated approximately 1,200 pounds of explosives in a rental van in the underground parking garage at the World Trade Center. The explosion created a five-story, 150-feet-wide crater, filled with 4,000 tons of rubble, in the sub-grade levels of the towers and undermined the floor of an adjoining hotel.

Hundreds of WTC tenants and visitors were trapped in elevators and on the observation deck, and thousands of others in the towers began to evacuate before first responders reached them. Within minutes, the North Tower lobby filled with thick black smoke. Reports of those trapped in the buildings soon overloaded the city’s 911 system.

Local, state, and federal agencies responded to the incident and contributed to what was then the largest coordinated rescue effort in New York City history. Some Port Authority of New York & New Jersey staff with specialized knowledge of the building remained in the towers to assist with the evacuation and rescue. New York City Police Department helicopters transported rescue personnel to the roof to assist in stairway evacuations of tenants on the upper floors.

The general evacuation of WTC tenants took more than four hours. Rescuers checked more than 200 elevator cars—freeing trapped people from 45 of them—and searched each floor of the World Trade Center complex, more than eight million square feet of space. Later that evening, 28 people with medical conditions, including one woman in labor, were escorted to the roof by NYPD and airlifted to an EMS staging area.