On Friday December 6, 1985, a natural gas explosion occurred at a restaurant in Derby, Connecticut. According to NFPA’s investigation, a gas main may have been damaged during the refilling of a sewer excavation. Before anyone became aware of the leak, escaping gas accumulated in the basement of the restaurant and came in contact with an undetermined ignition source. The explosion killed six people in the restaurant, injured 12 other occupants, and completely destroyed the building. Three people not in the restaurant were also injured by the explosion.
NFPA members can read the full investigation report.