Investigators picked their way through a gutted house Monday in Pendleton where five people died and two were seriously burned, but they found no initial indication of arson.
Pendleton Police Chief Stuart Roberts said that no cause had been ruled out.
The investigation began after daylight Monday because the two-story house was too dangerous to examine in the dark, he said.
“Pretty much all that’s left is the floor joists,” he said.
The two survivors are on breathing tubes at a Portland hospital and considered in critical condition, so authorities have not yet talked to them, he said.
The names of the victims haven’t been released. Roberts said authorities wouldn’t begin notifying relatives until the medical examiner’s office makes positive identifications.
Among the dead were three children.
Authorities told the East Oregonian newspaper on Sunday that the victims were from more than one family.
Local, state and federal investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives are doing the investigation.
The house, a rental, was old and burned rapidly, Roberts said.
“It’s probably a turn-of-the-century house, probably minimal insulation,” he said. “It went up pretty quickly.”
Pendleton is a city of about 16,700 people about 200 miles east of Portland.