A Cape Elizabeth man escaped injury Monday when his house exploded and caught fire.

Fire investigators said a leak in a propane line caused the explosion, which destroyed the home’s office and dining room – about half of the single-story ranch-style house at 146 Scott Dyer Road.

John Dorsey, 69, a Vietnam War veteran, happened to be sitting in his living room, at the other end of the house, when the explosion occurred. He fled to safety with his dog and called 911.

Dorsey’s wife, Sarah, was not at home when the fire broke out around 11:43 a.m.

“It was just like a bomb that went off,” Dorsey said in a telephone interview Monday night. “Afterwards, I thought, ‘Holy mackerel, what just happened?’ ”

The State Fire Marshal’s Office was called to investigate and determined there had been an explosion moments before the house caught fire.

“The concussion from the blast cracked the slab foundation, broke two legs off the dining room table, and knocked pictures off the walls,” said Chris Stanford, a senior investigator with the fire marshal’s office. He said Dorsey “was lucky because he spends a lot of time in his office.”

Stanford said the home’s propane tank is in the backyard, about 50 feet from the house. An underground line connects the tank to a regulator attached to the rear wall of the house. A 10-foot-long, horizontal propane line was clipped to the rear wall, about a foot above the ground. Snow and ice that had fallen off Dorsey’s roof severed the propane line, causing the gas to leak into the home.

The gas was concentrated in the area around the home office, where there were several electronic devices. One of those devices ignited the gas, Stanford said.

“I had been down to that part of the house just a few minutes before the explosion,” said Dorsey, who was doing a crossword puzzle in his living room when the gas exploded.

Dorsey said the explosion rocked his home. He fled with his landline telephone and called 911.

“I said, ‘I just had an explosion. I need help,'” he recalled.

Stanford said Dorsey had raked snow off his roof regularly. The propane line was severed near the ground, where ice and snow had piled up.

State Fire Marshal Joe Thomas said it is important for homeowners to keep their roofs clear of ice and snow. Propane lines can be damaged by falling snow or ice. “It’s not uncommon at all this time of year,” he said.

It’s also important to make sure that storage tanks, if they are next to the home, are shielded in some way.

Cape Elizabeth Fire Chief Peter Gleeson said firefighters from Scarborough and South Portland also responded to the fire.

“The homeowner said the house went boom,” Gleeson said. “The home suffered significant damage but it is still standing.”

Gleeson said Dorsey’s car, which was parked in the driveway, was not damaged.

Though the house is in a residential neighborhood, no other homes were threatened by the fire or blast.

Dorsey said he plans to live with his daughter at her home in Scarborough. He plans to meet with his insurance agent Tuesday, but doesn’t expect to be able to return to his home for at least three months.