BOISE, Idaho (AP) — Rafters along the popular Middle Fork of the Salmon River in central Idaho are being told to be prepared to share reserved camping spaces with other rafters or even firefighters because of a nearby wildfire.

U.S. Forest Service spokesman Mike McMillan says the lightning-caused Papoose Fire 40 miles west of Salmon through Sunday has burned about four square miles in rugged terrain above the river. He says it's so rugged ground fire crews for safety reasons haven't been used so far.

He says a sky crane helicopter that can drop 2,000 gallons is working on the fire. McMillan says the fire is burning through grass, brush and some timber on the steep slopes. He says old wildfires from previous years could help firefighters stop it from spreading.