The first terrorist attack on the World Trade Center occurred on February 26, 1993, at 12:17 p.m., when a Ryder truck filled with of explosives, planted by Ramzi Yousef, detonated in the underground garage of the North Tower. The blast resulted in a hole through five sublevels. The greatest damage was on levels B1 and B2, with significant structural damage on level B3. Six people were killed, and more than a thousand were injured, as 50,000 workers and visitors were inside the tower at the time. Many people inside the North Tower were forced to walk down darkened stairwells that had no emergency lighting, and some took two hours or more to reach safety.