( CNN ) -- Human error is to blame in last week 's gas-fueled explosion that ripped through a strip club in the western Massachusetts city of Springfield , officials said Sunday . The blast injured at least 21 people , including firefighters . A utility worker , responding to a report of a gas odor inside a building , inadvertently punctured a hole in a high-pressure gas line at the foundation of that building , according to a statement from the Office of the State Fire Marshal . Markings on the sidewalk incorrectly indicated where the line was . Once the pipe was punctured , the worker called the gas company and the fire department to shut off the gas , and the area around the building was evacuated . Investigators believe gas from the leak entered the building and later ignited . `` They ( investigators ) have determined that human error as opposed to a fault of the gas infrastructure provided the fuel for the explosion . Exactly whose human error will be the subject of the Department of Public Utilities ' ongoing investigation , '' the statement read . The blast occurred at 5:25 p.m.Friday . Twelve of the 14 firefighters on scene were injured , according to Springfield Fire Commissioner Joseph Conant . `` All have been treated and released but several will face a long recovery road , '' he said . Four gas company employees , two police officers , a municipal water and sewer department employee and two civilians were also injured , according to the city 's mayor . People as far away as South Hadley , 10 miles north , felt the blast . Video showed that the facade of one building was shredded by the blast , while glass from blown-out windows littered streets blocks away . Besides the leveled multistory structure that housed Club Scores , 12 buildings suffered significant damage , and at least a dozen others had collateral damage , Conant said .
A construction worker inadvertently blew a hole in a gas line in Cambridge , Massachusetts . Fire ##s : Markings on the sidewalk incorrectly indicated where the line was . At least 21 people were injured in the blast , including firefighters .