Investigators believe a man lighting a cigarette triggered a natural gas explosion in Old Town Bend early Thursday that destroyed his house, damaged two nearby homes and sent him to the hospital with serious injuries.

Michael Monroe Flint, 61, was at the Legacy Oregon Burn Center in Portland in critical but stable condition as of 7:30 p.m. Thursday.

Firefighters responded to 337 N.W. Georgia Ave. just before 4 a.m., where they found a small cottage engulfed in flames and two houses on either side beginning to catch fire. A crew of 19 firefighters evacuated nearby homes and brought the fire under control in about an hour.

Ryan O’Toole, who lives in the larger house on the same property, was in bed about 10 feet from Flint’s wall when he heard the explosion.

“It sounded like a plane crashed, like a huge bomb went off,” O’Toole said.

O’Toole realized there was a fire and began putting on his clothes when he heard Flint pounding on his door.

“He said ‘Call 911′ and kind of fainted on the grass,” O’Toole said.

O’Toole picked up a garden hose and attempted to fight the fire. Police arrived and told him to back away from the fire, O’Toole said, but he briefly ran back into his burning home to look for his dog. The dog was found unharmed a few houses away, O’Toole said.

Although only one corner of his house burned, O’Toole said it appears fire or smoke damage destroyed all his possessions except for the food in his refrigerator.

Deputy Fire Marshal Susie Maniscalco said Thursday’s investigation suggests the connection between the gas line to the furnace in the living room of the cottage was not secure, allowing a significant quantity of gas to accumulate and ignite when Flint lit his cigarette.

The explosion sent pieces of glass and other pieces of the cottage flying, she said, with debris found up to 150 feet away and on the roofs of nearby homes.

Dan Mahoney, owner of the two rental units, said he was at Flint’s cottage the afternoon before the explosion and didn’t observe anything out of the ordinary. Flint had lived in the cottage for about a year, Mahoney said, and works as a cabinet maker.

“It’s just a tragedy. Michael — the tenant back there — he’s in our prayers big time,” Mahoney said. “These are not only people we rent to, they’re people we care about.”

Neighbor Erin Scott said she didn’t realize anyone lived in the cottage across the street until early Thursday.

“I was dead asleep. I woke up and knew there was a really loud boom,” Scott said. “I woke up thinking, ‘What in my house is big enough to fall over and make that big a boom?’ It sounded like a huge bookshelf falling over.”

Scott noticed flickering through her blinds and went outside to see flames climbing roughly 40 feet into the trees surrounding Flint’s and O’Toole’s houses. She later discovered the force of the explosion had knocked over empty beer bottles inside her house, and learned that a co-worker living four blocks away had also been awakened by the noise.

Susan Prowell, who lives directly behind Flint and whose home was scorched by the flames, heard a comparatively small sound — she assumed raccoons had knocked over her birdbath, as had happened about three weeks earlier. Seeing flames outside her bedroom window, Prowell and a houseguest evacuated, finding more than a dozen neighbors gathered in the street.

Although her home sustained the least damage of the three involved, Prowell, 62, said she’s been besieged by phone calls and visits from friends and neighbors wanting to know how she’s doing. Such closeness is typical of the neighborhood, she said, adding that even those who didn’t know Flint and O’Toole are concerned about the two men.

“It’s a neighborhood of fine neighbors, good people, supportive people, action-oriented people,” Prowell said.