GAITHERSBURG, Md. — Federal investigators said Thursday that they have solved one mystery of the attacks on Sept. 11, 2001: the collapse of World Trade Center Building 7.
The 47-story building north of the World Trade Center’s towers was set on fire by falling debris from the twin towers and collapsed seven hours later. Scientists with the National Institute of Standards and Technology said their three-year investigation determined that the demise of WTC 7 was actually the first time in the world that a fire caused the total failure of a modern skyscraper.
Investigators concluded that the collapse of the towers broke a city water main, leaving the sprinkler system in the bottom half of the building without water. Fire then destroyed supports for a critical column whose collapse brought the building down.
Sunder said his team probed suspicions that an explosion inside the building brought it down but found no evidence of it.
