A house boat fire that seriously injured a 41-year-old Forsyth County man Sunday remains under investigation, though authorities say it does not appear suspicious.

Forsyth County Fire Capt. Jason Shivers said the man, whose name has not been released, suffered second- and third-degree burns to his upper body and extremities.

Shivers said the man was flown to Grady Memorial Hospital in Atlanta, where he was listed Tuesday in stable condition.

He said the flames destroyed the 72-foot, two-story yacht, which was beached at an unnamed island on Lake Lanier when the fire broke out.

Fire and emergency personnel responded about 3:30 p.m. Sunday to Long Hollow Park, which Shivers said is near the island in northeastern Forsyth.

“The first phone call came from Gainesville Marina [in Hall County],” he said, adding that is where the boat is typically docked.

There were nine people on the boat. Shivers said the man was burned while helping the others get out.

Teresa Bennett watched the blaze from her home on the lake.

Bennett, who lives on the Hall side, said she used her binoculars and saw that the front end of the boat was on fire.

“It looked to me like somebody’s barbecue got out of hand, just from the size of it,” she said.

But Bennett called 911 after talking to her neighbor, who had determined the fire was worse than they first thought.

Bennett said the boat erupted while she was on the phone.

“Kaboom!” she said. “It was like a huge explosion. I could hear the windows in my house shake behind me.”