New York, Aug.22 : American federal investigators are claiming that they have solved a mystery of the Sept. 11, 2001 attacks: the collapse of World Trade Center building 7, a source of long-running conspiracy theories.
The 47-story trapezoid-shaped building sat north of the World Trade Center towers, across Vesey Street in lower Manhattan. On September 11, 2001 it was set on fire by falling debris from the burning towers.
CBS quoted an Indian-American scientist, Dr. Shyam Sunder of the National Institute of Standards and Technology, as saying that a fire caused the total failure of a skyscraper.
Investigators also concluded that the collapse of the nearby towers broke the city water main, leaving the sprinkler system in the bottom half of the building without water.
The building has been the subject of a wide range of conspiracy theories for the last seven years, partly because the collapse occurred about seven hours after the twin towers came down. That fueled suspicion that someone intentionally blew up the building in a controlled demolition.
Critics like Mike Berger of the group 9/11 Truth said he wasn't buying the government's explanation.
"Their explanation simply isn't sufficient. We're being lied to," he said, arguing that there is other evidence suggesting explosives were used on the building.
Sunder said his team investigated the possibility that an explosion inside the building brought it down, but found there was no large boom or other noise that would have occurred with such a detonation.
The investigators also ruled out the possibility that the collapse was caused by fires from a substantial amount of diesel fuel that was stored in the building, most of it for generators for the city's emergency operations command center.
The 77-page report concluded that the fatal blow to the building came when the 13th floor collapsed, weakening a critical steel support column that led to catastrophic failure.