As the North Tower collapsed, debris hit 7 WTC "with the force of a volcanic eruption."[18] Much of the bottom 10 stories of the building's south face were destroyed, with damage visible as high as the 18th floor. A massive fire burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, with flames visible on the east side of the building.[19][20] Around 2 o'clock in the afternoon, firefighters noticed a bulge in the southwest corner of 7 World Trade Center, between the 10 and 13th floors, which was a sign that the building was unstable and might collapse.[21] During the afternoon, FDNY Chief Daniel Nigro made the decision to halt rescue operations, surface removal and searches along the surface of the debris near 7 World Trade Center and evacuate the area, out of concerns for the safety of personnel.[22] At 5:20 p.m. EDT on September 11, 2001, 7 World Trade Center collapsed. The building had been evacuated and there were no casualties associated with the collapse.
