Examination of hundreds of structural steel components from WTC buildings.Extensive reviews of design, construction, maintenance and inspection documents for the buildings.Interviews with 1,056 surviving occupants of the WTC buildings and 116 emergency responders.More than 200 professionals and technical subject matter experts, including 85 NIST staff members, answered the call and participated in the investigation.Īs part of the investigation, the NIST team gathered every bit of evidence they could find. NIST was given this authority when Congress passed, and the President signed into law, the National Construction Safety Team Act of 2002.
NIST responded to calls from Congress and the public to carry out a federal investigation of why the buildings collapsed, the evacuation of building occupants and the emergency response. The collapse of the WTC buildings following the terrorist attacks on September 11, 2001, was one of the worst building disasters in US history, killing 2,749 people, including 400 emergency responders.
