At 12:17 p.m. on February 26, 1993, an explosion rocked the 110-story twin World Trade Center towers, caused by a powerful bomb - the equivalent of more than a thousand pounds of TNT, located in a parked van on the B-2 level of the underground garage near the foot of the North Tower.

People working inside felt the building move, but didn't know what was happening, according to reports. No alarm bells sounded. No public address announcements were made. Workers didn't know if they should evacuate or stay in the building.