Ayer Explosion Kills 1, Injures 3 Others

AYER, MA — One employee at the building where an explosion occurred late Friday afternoon has died, the Middlesex District Attorney's Office confirmed Saturday morning. Another employee an two firefighters suffered injuries.

The explosion occurred at Advanced Vacuum Systems on Fitchburg Road around 5:15 p.m., giving way to a four-alarm fire. Two employees were transported to the hospital. One employee, a man in his 50's who has not been identified, was later pronounced dead.

The explosion was caused by an apparent pressure vessel malfunction, the DA's Office said.

There was no word on the condition of the other employee. Two mutual aid firefighters had minor injuries.

The man's death is not considered suspicious. The Occupational Safety and Health Administration is among those investigating.