WASHINGTON, Maine — Investigators are not able to determine the cause of a house fire that killed a father and son last week in the town of Washington, according to a state official.

Because of “severe damage to the house” investigators cannot identify what caused a fire to break out at the Cattle Pound Road home on the morning of Jan. 23, Maine Department of Public Safety spokesman Stephen McCausland said Monday in a statement.

The state fire marshal’s office believes the blaze “started in the basement near the wood stove,” according to McCausland.

“Investigators say there is nothing to indicate the fire is anything but an accident,” McCausland said.

A family of three was in the house at the time of the fire. Steven Rhodes, 53, and his son, Isaac Rhodes, 25, died in the blaze. Elizabeth Rhodes, 56, Steven Rhodes’ wife and Isaac Rhodes’ mother, survived and was treated for smoke inhalation and burns at Maine Medical Center in Portland.

According to investigators, Steven Rhodes unsuccessfully tried to put the fire out and then fled the home, only to discover that Isaac Rhodes was still inside.

“Rhodes went back inside the burning house to find his son, and both men were overcome by the smoke and heat,” McCausland said.