LEWISTON, Idaho (AP) — Five structures have been destroyed by a wildfire burning in northern Idaho and fire managers on Thursday planned a burnout operation to halt the fire's northeast expansion.

Big Cougar Fire spokesman Tom Rhodes says it's unclear if the destroyed structures are homes or outbuildings in the remote area accessible only by boat. The fire is on the east side of the Snake River across from Oregon and Washington state. Rhodes says about 160 structures are threatened by the 64-square-mile fire burning in mostly grass but also some timber.

Residents have been told to evacuate. No injuries have been reported. About 319 firefighters plus four helicopters are fighting the lightning-caused blaze that started Saturday. Rhodes says the Snake River is preventing the fire from reaching Oregon and Washington.