(CNN) -- Firefighters in Washington have contained a massive blaze that started on one house's roof and spread to at least 15 other homes, authorities said.
Stacked logs at a saw mill were also engulfed by the fire and helped fuel the flames, Yakima County Fire Chief George Spencer said late Saturday.
"We're talking thousands and thousands of logs. It'll take about three or four days for that to burn out," he said.
Authorities said the fire started around 2 p.m. Saturday in the town of White Swan, located on the Yakama Indian Reservation.
Investigators do not know what caused the fire, Sgt. George Town of the Yakima County Sheriff's Office said.
Firefighters have not official determined what sparked the blaze, but are considering it to be accidental, Spencer said.
He said the fire may have destroyed or damaged at least 15 and as many as 20 homes.
At least 60 firefighters from 12 different fire departments battled the flames for more than eight hours.
Two firefighters sustained minor injuries and were treated at the scene.