Authorities believe the cause of the fire that destroyed a mobile home on Mammoth Road on Aug. 17 was accidental, although the blaze remains under investigation.

According to Fire Chief James Midgley, the fire ignited somewhere in the right rear portion of the mobile home, but officials are still trying to determine what set it off. No one was home when the fire broke out sometime before 6:01 p.m., though the resident of the 556 Mammoth Road mobile home arrived shortly afterward, Midgley said.

According to officials, the resident was later transported to the Southern New Hampshire Medical Center in Nashua after suffering serious injuries trying to free his dog from the fire. Midgley said the resident tried to break through a glass door and sliced open his arm in the process. Officials are still trying to locate the dog, according to Midgley.

Authorities are not releasing the name of the resident, though Kevin Edwards is listed under the phone number for the address on yellowpages.com.

Midgley said the fire spread quickly, consuming much of the mobile home in the roughly seven minutes it took his department to respond to the initial report. According to Midgley, mobile home fires are some of the most dangerous fires to fight.

“(The fire) went fast ... The mobile home is constructed out of lightweight stuff and there is not a whole lot of insulation to contain the fire,” he said. “By the time the call was placed the fire had ripped through the place.”

Firefighters had the blaze under control at 6:21 p.m., according to officials.

Pelham received mutual aid from the nearby communities of Hudson, Windham, Salem, Litchfield and Dracut, Mass. Derry and Londonderry covered the fire station during the fire, Midgley said.