'Human error' blamed for gas explosion that damaged more than 40 buildings in Springfield, Mass. Jessica Hill / AP Inspectors stand in debris Saturday at the site of a gas explosion that leveled a strip club in Springfield, Mass., on Friday evening. A powerful natural gas explosion that leveled a strip club, damaged 41 other buildings and injured about 20 people in Springfield, Mass., was triggered when a utility worker accidentally punctured a pipe, authorities announced on Sunday. "Human error ... is what the cause of the explosion was," Massachusetts Fire Marshal Stephen D. Coan said at an afternoon news conference. Officials said a worker for Columbia Gas Co., responding to a call Friday evening about a gas odor in a building on Worthington Street in the city's entertainment district, was using a metal probe to try to find the leak. He accidentally punctured an underground pipeline, causing gas to rush out, and an unknown spark triggered the powerful explosion. The blast flattened Scores Gentlemen's Club, heavily damaged a day care center, shattered windows and scattered debris over several blocks. Scores and other area buildings had been evacuated before the blast, according to The Republican newspaper. Some officials called it a miracle that no one was killed. Most of the injured were part of a group of gas workers, firefighters and police officers who ducked for cover behind a utility truck just before the blast. Part of the neighborhood already had been evacuated because of reports of a gas leak and odor. Preliminary reports showed the blast damaged a total of 42 buildings housing 115 residential units. Three buildings were immediately condemned, and 24 others require additional inspections by structural engineers to determine whether they are safe, according to The Associated Press. Roughly 20 people were injured. None of the injuries was considered life-threatening. Springfield, which is 90 miles west of Boston and has about 150,000 residents, is the largest city in western Massachusetts. It's known as the home of the Basketball Hall of Fame, which is not near the blast site. The city has been rebuilding from damage caused by a tornado in June 2011.