1 dead in Ayer explosion felt a mile away; 2 firefighters injured

The latest breaking updates, delivered straight to your email inbox.

A man is dead after an industrial furnace exploded around 4:30 p.m. Friday. Residents said they could hear the explosion from a mile away.

"It was just a big boom -- a big loud boom, like thunder or like a transformer blowing," said Becky Brennan.

"It just was a sudden boom. A one-time thing, a one-shot event," said Alan Friot.

The explosion and resulting fire occurred at 60 Fitchburg Road, inside Advanced Vacuum Systems, police said. The company's website said they manufacture "vacuum and pressure furnaces."

"When the explosion occurred, it blew whatever was on fire, it blew it up to the corners of the building, so we had fires around the roofline," explained Chief Robert Pedazzi of the Ayer Fire Department.

Three employees were hurt, including one person who suffered burns over a quarter of his body. The Middlesex District Attorney's Office said one of those employees, a man in his 50s, was later pronounced dead. Two firefighters also suffered minor injuries while working on the three-alarm fire.

Route 2A was closed for several hours as the firefighters worked.

The cause of the explosion and fire is not yet known. It is under investigation by OSHA and the office of the Massachusetts State Fire Marshal.

"The investigation is ongoing but preliminary findings point to a failure of a pressure vessel," said Jennifer Mieth, spokeswoman for the Department of Fire Services.