A third tower at the World Trade Center site collapsed due to a fire, not explosives, on the afternoon of September 11, 2001, a news report said Friday, according to dpa. The 47-storey tower tumbled seven hours after the center's twin towers were attacked by terrorists. No one died as the approximately 4,000 officer workers had been evacuated. An investigation by the National Institute of Standards and Technology (NIST), based in Maryland, has revealed that tower 7 collapsed after fires ravaged floor beams and a structural column, the New York Times reported. At the time, tower 7 housed branch offices of the Central Intelligence Agency, the Secret Service and the New York mayor's emergency operations centre. It was located 400 feet north of the twin towers. NIST used photographs, building design documents and videos to create a computer model of the tower and find out what triggered its collapse. There has been much speculation about the collapse of tower 7, after the World Trade Center's 110-storey twin towers were destroyed by terrorist attacks that killed more than 2,700 people. The theories ranged from an insider planting explosives to blast the third tower to the presence of diesel tanks installed to power generators. "Our take-home message today is the reason for the collapse of World Trade Center 7 is no mystery. It did not collapse from explosives or fuel oil fires," lead investigator B Shyam Sunder was quoted as saying. NIST's 915-page report was released after three years of study by more than 50 federal investigators. Many dismissed the investigation as seriously flawed. "How much longer do we have to endure the cover-up of how building 7 was destroyed?" the paper quoted Richard Gage, leader of a group called Architects for 9/11 Truth, as saying.
