OSAGE BEACH, Mo. (AP) — Missouri’s fire marshal says investigators are not able to determine the cause of an August fire in Osage Beach that killed four children.

A fire investigator’s report released Tuesday found the damage was so extensive he could not determine whether the fire was started by cigarette butts in a can or by electrical wiring from an air conditioning condenser on the condo’s landing. The can was on the floor of the landing between the condenser and a wall.

The children killed in the fire at the Compass Pointe Condominiums ranged in age from two to five. They were in bed when the fire broke out. An adult with them escaped and said he tried to return to rescue the children but became disoriented.