SPRINGFIELD, Mass. (CBS/AP) ? Authorities in western Massachusetts announced on Saturday that human error was to blame for a blast that leveled a strip club, damaged 42 buildings, and injured 21 people in Springfield’s entertainment district.

State Fire Marshal Stephen Coan said a gas company worker responding to reports of a gas leak punctured a pipe that eventually led to a massive explosion.

Officials said on Sunday that a Columbia Gas employee arrived Friday evening to investigate the report for an odor of gas. It is unclear what prompted that initial call.

The state fire marshal said that worker was using a metal probe to look for the source of a possible leak, and punctured a line that was improperly marked.

It took 20 to 30 minutes to shut off the line. During that time, the area was evacuated.

A large amount of natural gas seeped into the building that eventually exploded.

Authorities on Sunday did not name the worker who caused the blast.

Columbia Gas planned a news conference for 4 p.m. to respond to the developments.

Friday’s afternoon’s explosion flattened a strip club and heavily damaged a day care center at about 5:30 p.m., after officials had already evacuated part of the entertainment district because of reports of a gas leak and odor.

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.

The explosion blew out windows and scattered debris over several blocks.

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