The 47-story tower collapsed seven hours after the Twin Towers and it has become the subject of heated speculation and a host of conspiracy theories which suggest it was brought down by a controlled demolition.
Nearly seven years on, the final official report on the World Trade Center is due to be published in July.
Official investigators are expected to conclude that fire caused the collapse of this third tower at the World Trade Center. But that makes this the first and only skyscraper in the world to collapse solely due to fire.
The Conspiracy Files explores many unanswered questions to try to find out what really happened, and why some people think there was a sinister plot to destroy the building.
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