Fire Collapsed WTC 7: Report

Fires, not explosives, caused the collapse of World Trade Center 7—a skyscraper near the twin towers—on Sept. 11, a 3-year US government investigation concludes. Scientists with the National Institute of Standards and Technology say the 47-story tower was destroyed by fires, made worse by a failed sprinkler system after the crumbling twin towers broke a city water main, the AP reports.

Conspiracy theorists have long blamed the fall of WTC 7 on other reasons, including bombs placed internally. The government report also indicates that the collapse of the building is the only known instance of fire leading to the total failure of a skyscraper. (More World Trade Center stories.)