officially recorded the casualties of the 9/11 attacks in their crime statistics for 2001, with the FBI stating in a disclaimer that "the number of deaths is so great that combining it with the traditional crime statistics will have an outlier effect that falsely skews all types of measurements in the program's analyses." Evacuation Most tall buildings in the United States at the time were not designed for complete evacuation during a crisis, even after the 1993 World Trade Center bombing. It was also procedural for announcements in the case of high-rise fire safety for individuals to remain in their offices unless they were near the burning floor. However, after it took ten hours to completely evacuate the towers in the 1993 attacks, multiple additions were made to the buildings and evacuation plans. Radio repeaters were installed in the towers to improve communication, battery powered emergency lights were installed, and fire drills held. Individuals who evacuated for both the 1993 and 2001 attacks reportedly stated they were better prepared for the 2001 evacuations. At least two individuals who had evacuated in both 1993 and 2001 later reported that they had prepared for a potential evacuation after 1993, by bringing either an item such as a flashlight or an emergency preparedness bag with them. The two World Trade Center buildings housed three stairwells in the center core of each tower. At floors containing lift and ventilation machinery (such as some of the floors where Flight 175 struck WTC 2), the northern and southern stairwells entered corridors extending north and south to stairwells that bypassed the heavy machinery. The three stairwells were labeled A, B, and C, and were as tall as the buildings with two built to in width and the third being wide. In the North Tower the stairs were approximately 70 ft apart, compared to the about 200 ft in the South Tower. At the time of the attacks, media reports suggested that tens of thousands might have been killed. Estimates of the number of people in the Twin Towers when attacked on Tuesday, September 11, 2001, range between 14,000 and 19,000. The National Institute of Standards and Technology estimated that approximately 17,400 civilians were in the World Trade Center complex at the time of the attacks. Turnstile counts from the Port Authority indicate that the number of people typically in the Twin Towers by 10:30 am was 14,154.