WASHINGTON, Maine (AP) — Maine fire officials say the exact cause of a fire that killed a father and son cannot be determined because of the extent of damage to the house.

Fifty three-year-old Steven Rhodes and his 25-year-old son, Isaac Rhodes, died in the Washington fire earlier this month. The State Fire Marshal’s Office says on Monday there’s nothing to indicate the fire was anything other than an accident.

Authorities say the fire started in the basement of the home near a wood stove. Investigators say Steven fled the building and went back into the burning house when he realized Isaac had not escaped. Both men were then overcome by smoke and heat.