COLEBROOK, N.H. – Multiple explosions at a gun and ammunition manufacturing plant in far northern New Hampshire on Friday killed two people, shook buildings blocks away, filled the sky with black smoke and forced the evacuation of dozens of homes.

State Fire Marshal Bill Degnan confirmed the deaths at the MDM Muzzleloader building in Colebrook. He said the two victims, along with another person who received minor injuries, were the only people in the building at the time.

The blasts started just after 1 p.m. and continued for at least two hours as ammunition exploded, said Mia West, Colebrook’s public information officer. She said firefighters initially were unable to get close enough to fight the blaze because ammunition was still going off more than two hours after the first blast.

“We did hear two distinct bangs,” said Karen Ladd, editor and publisher of The News and Sentinel newspaper in Colebrook. She thought something had hit the roof of her building. “It knocked a picture off of my wall, right next to my desk. I will admit I panicked and I said, ‘Get out!”‘

Degnan said the fire continued to burn more than four hours after the explosion was reported, and that it was too soon to determine the cause.

“We’re just getting into the investigation and trying to determine the details,” he said.

About 40 nearby homes were evacuated, and some residents reported hearing the explosion more than a mile away, West said. Displaced residents were offered accommodations at The Balsams Grand Resort and Hotel in nearby Dixville Notch.

Several communities in New Hampshire and Vermont sent fire crews.

“It’s just major, major explosions and black powder,” said Mishel Fenn, a bartender at the Colebrook House motel, who felt the blast two blocks away. “It shook the building, and I’m in a large building.”

Calls to company officials were not immediately returned Friday.