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 . `` They ( investigators ) have determined that human error as opposed to a fault of the gas infrastructure provided the fuel for the explosion . At least 21 people were injured in the blast , including firefighters .
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 .