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On September 11, 2001, 2,996 innocent civilians were killed during one of the deadliest attacks in American history. On 8.45am, a hijacked American passenger Boeing 767 crashed into the north tower of the World Trade Centre in New York City. The aircraft loaded with 20,000 gallons of jet fuel struck near the 80th floor of the 110-story skyscraper.

Just 18-minutes later a second Boeing 767 - United Airlines Flight 175 hit near the 60th floor of the south tower. Less than two hours after the first tower was hit, at 9.59 am, the south tower collapsed in just under 10 seconds - 29 minutes later the north tower collapsed to the ground - just 102 minutes after being hit. However, the mystery surrounding the third tower known as Tower Seven (WTC7) has been central to many conspiracy theory’s because the skyscraper fell to the ground without being hit by a plane. The 47-storey third tower, located 110 meters (350 feet) away from the World Trade Centre, collapsed seven hours after the twin towers.

On September 11, 2001 the twin towers were struck by two passenger aircrafts

Researchers have dismissed the findings of Government officials in 2008 that the building fell due to “uncontrolled building fires”. Following an extensive four-year study at the University of Alaska, using four extremely complex computer models, Dr. Leroy Hulsey, Dr. Zhili Quan, and Professor Feng Xiao found the “fire did not cause the collapse”. In their report, it says: “The principal conclusion of our study is that fire did not cause the collapse of WTC 7 on 9/11, contrary to the conclusions of NIST [National Institute of Standards and Technology] and private engineering firms that studied the collapse. “The secondary conclusion of our study is that the collapse of WTC 7 was a global failure involving the near-simultaneous failure of every column in the building.”

On 8.45am a hijacked American passenger Boeing 767 crashed into the north tower of the World Trade Centre

Meanwhile, a leading conspiracy theorist has also dismissed the official's findings, Robert Korol, a civil engineering professor and joint author of the Architects & Engineers for 9/11 Truth, claims the destruction of the tower was caused by “controlled demolition”. Theorists have also been sceptical about the occupants of the building as two of the floor were believed to be home to the secret service. Mr Korol said: “I just couldn’t understand how those buildings collapsed. It didn’t make sense. He added: “Indeed, neither before nor since 9/11 have fires caused the total collapse of a steel-framed high-rise — nor has any other natural event, with the exception of the 1985 Mexico City earthquake, which toppled a 21-storey office building. “Otherwise, the only phenomenon capable of collapsing such buildings completely has been by way of a procedure known as controlled demolition, whereby explosives or other devices are used to bring down a structure intentionally.” READ MORE: 1,100 victims of World Trade Center attack still not identified

Aerial footage of the collapse of the twin towers

The leading professor also claims the fires would have not been strong enough to burn through the steel structures. He added: “The fires were on the upper floors, there’s little chance the heat would have spread down and caused the steel columns, or the connectors or floor beams, to sufficiently weaken and collapse in the twin towers. “Also they were treated with a fire retardant which would have insulated them.” In 2008 The National Institute of Standards and Technology (NIST) in charge of the official report concluded fire was the explanation for the collapse. DON'T MISS REVEALED: US ambassador to UK’s wife almost died in 9/11 [INSIGHT]

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The twin towers collapsed 102 minutes after being struck

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