BOSTON -- A fire that killed a mother, her son and the family dog in a Raynham mobile home early Monday morning was accidental, fire officials said.

Fire crews were called to the three-alarm fire at 92 Peter St., about 2:20 a.m.

They said the pair was found in the master bedroom and it appeared the son had gone in to try to rescue his mother and they became trapped and were killed, Raynham Fire Chief James Januse said.

Neighbors identified the pair as Dorothy Borham, 83, and her son, Neil, 61. Their dog, Butch, was also killed. Fire officials have not confirmed the victims' identities.

"I heard a crash or something and an explosion or something and I saw this big red-orange glow, and I said, 'My dear God.' The whole back was on fire. I ran around the house to turn the faucet on, my hose is on this side, and I start spraying, but it didn't do a bit of good," neighbor Madelaine Castelluzzo said.

Officials said careless smoking likely sparked the blaze.

“It appears that the fire started in the deck area behind the home, an area where smoking took place and, more than likely, improper disposal of smoking material started the fire,” Fire Marshal Stephen Coan said in a release.

Initially, fire investigators thought the fire was ignited by two 500-gallon propane tanks.

"They were afraid the propane tanks were going to explode, and they didn't want us in the area," neighbor Linda Bridgewood said.

"There is a safety valve (on the tanks) that blew off and it and just kept fueling the fire," Januse said.

It took firefighters two to three hours to get the flames under control.

"It is terribly sad. It started about 2 o'clock this morning and it was about 4 before they really got it out," neighbor Judy Westgate said.

Januse said the home was not equipped with smoke detectors.