 In November 2008 , NIST released its final report on the causes of the collapse of 7 World Trade Center . This followed NIST 's August 21 , 2008 , draft report which included a period for public comments . In its investigation , NIST utilized ANSYS to model events leading up to collapse initiation and LS @-@ DYNA models to simulate the global response to the initiating events . NIST determined that diesel fuel did not play an important role , nor did the structural damage from the collapse of the Twin Towers or the transfer elements ( trusses , girders , and cantilever overhangs ) . The lack of water to fight the fire was an important factor . The fires burned out of control during the afternoon , causing floor beams near column 79 to expand and push a key girder off its seat , triggering the floors to fail around column 79 on Floors 8 to 14 . With a loss of lateral support across nine floors , column 79 buckled – pulling the east penthouse and nearby columns down with it . With the buckling of these critical columns , the collapse then progressed east @-@ to @-@ west across the core , ultimately overloading the perimeter support , which buckled between Floors 7 and 17 , causing the remaining portion of the building above to fall downward as a single unit . The fires , fueled by office contents , along with the lack of water , were the key reasons for the collapse . 
