NIST Final Report on WTC 7 Collapse Released

NIST concludes that WTC 7 collapsed due to fires on multiple floors ignited by debris from the North Tower's collapse. The fires burned without suppression because the building's water supply had been exhausted. A key finding is that 'thermal expansion' caused a critical column to fail, initiating a progressive collapse. NIST concludes 'the collapse was primarily due to fires' and not to any pre-planted explosives. This is the first time NIST attributed a major skyscraper collapse primarily to fire.