A Springfield, Mass., strip club exploded Friday evening after a gas-company worker's metal probe punctured a natural-gas line and caused the club to fill with gas, investigators said Sunday.

Officials may never know exactly what sparked the explosion, which flattened the club, damaged dozens of nearby buildings and injured 19 people, including 12 firefighters who had rushed to evacuate the building and area.

According to the findings of an investigation by Massachusetts State Fire Marshal Stephen D. Coan, an employee with the Columbia Gas Co. was responding to a report of a gas odor at the Scores Gentleman's Club in downtown Springfield and was looking for the source.

"The gas company employee smelled gas at the threshold of the building, but metered no gas inside," Coan's office said in a news release. "He began to search outside the building using a metal probe to make holes in order to measure gas. His examination appears to have been an appropriate distance from where older markings on the sidewalk indicated where the gas line was. However, the markings were incorrect and his metal probe inadvertently punctured the high-pressure gas line right at the foundation of the building."

The employee called the fire department and told his company to shut off the gas, which was filling the building. Springfield Fire Commissioner Joseph Conant said firefighters' evacuation of the scene saved many lives.

A spokeswoman for the Columbia Gas Co. did not respond to a request for comment.