Laconia, NH- LACONIA — Fire investigators say the ignition of propane gas from an open pipe was the cause of a Thursday explosion that left a Lakeport residence looking like a bomb scene.

Fire Chief Ken Erickson said the blast at 56 Chapin Terrace occurred when an oil-fired furnace ignited a gas leak that appears to have resulted when an occupant of the home was remodeling the kitchen.

Matilda Woodward, 81, and her son, Richard, were at her home on Lake Opechee when the house exploded at approximately 1:25 p.m.

While both were fortunate to walk away uninjured, the house sustained severe structural damage when pressure from the blast blew apart much of its cinder-block foundation. The explosion also blew out all the windows in the home and had enough force to blow the front door and a rear picture window out.

The blast caused little fire damage, but did leave the home uninhabitable.

Erickson said investigators quickly linked the blast to the area of the basement where they found more significant damage and the remnants of five small fires.

The chief said they now believe that the explosion occurred as a result of a sheered half-inch copper propane line that leaked gas into the basement.

Erickson said officials believe the leak occurred on Thursday while Richard Woodward was moving a stove to remodel his mother’s kitchen.

The chief said Woodward smelled propane earlier in the day while working, but thought nothing of the problem after opening door and windows for a period.

However, he pointed out that propane is almost three times heavier than air and most of the gas settled in the basement of the home.

“They thought they were safe, but in reality they had a basement full of propane,” explained Erickson.

The chief said so much gas was leaked into the basement that it displaced oxygen, and that prevented an initial explosion. However, as it dissipated it became combustible, he said.

Erickson said the gas is believed to have been ignited when an oil-fired furnace kicked on to support a water heater.

Investigators are unsure of exactly how long the propane line was open, but say the tank was nearly empty.

The chief said the house is uninhabitable due to structural problems with the foundation. He said the inside of the home also sustained substantial damage when the blast sent objects flying and also blew out portions of its wallboard.

Erickson said the home will either need to be lifted up to provide a new foundation or completely torn down. The chief suspected that the home could also have wiring damage that could need to by fixed to prevent fire danger.