 After the North Tower collapsed , some firefighters entered 7 World Trade Center to search the building . They attempted to extinguish small pockets of fire , but low water pressure hindered their efforts . Over the course of the day , fires burned out of control on several floors of 7 World Trade Center ; the flames visible on the east side of the building . During the afternoon , fire was also seen on floors 6 – 10 , 13 – 14 , 19 – 22 , and 29 – 30 . In particular , the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon . At approximately 2 : 00 pm , firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors , a sign that the building was unstable and might collapse . During the afternoon , firefighters also heard creaking sounds coming from the building . Around 3 : 30 pm , FDNY Chief Daniel A. Nigro decided to halt rescue operations , surface removal , and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel . According to FEMA , the building started to collapse at 5 : 20 : 33 pm EDT when the east mechanical penthouse started crumbling , but differing times are given as to what time the building completely collapsed — at 5 : 21 : 10 pm EDT according to FEMA , and at 5 : 20 : 52 pm EDT according to NIST . There were no casualties associated with the collapse . 
