WASHINGTON, Maine — State 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.

Steven Rhodes, 53, and his son Isaac Rhodes, 25, died in the fire last week in the Knox County town of Washington. The state Fire Marshal’s Office said Monday that 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 in when he realized that Isaac had not escaped. Both men were then overcome by smoke and heat.