PORTLAND (AP) - The terrain is so rough that crews battling a growing grass fire in the breaks of the Hells Canyon Recreation Area have taken to sleeping out in the wilderness rather than rough riding back to camp at night.

The firefighters call it “coyote camping,” said Dave Schmitt, a spokesman for the force of more than 600 personnel working on a fire along the Imnaha River as it runs north into Hells Canyon.

Schmitt said Monday that several crews on the Battle Creek fires have chosen not to return to the main camp at the Wallowa County Fairgrounds in Enterprise.

“There are a couple of crews have been out there five days,” he said.

The Battle Creek fire was burning on about 37,000 acres Monday, or about 58 square miles. The terrain is so steep and rocky that crews are having trouble finding a place to dig lines to contain the fire, Schmitt said.

About 100 homes on the other side of a ridge from the Battle Creek fire are considered threatened, but nobody had been evacuated Monday.

Schmitt said there's nothing inhabited for a great distance north of the fire.

Statewide, firefighters reported 13 major blazes totaling about 350,000 acres - 546 square miles. Six of the fires were considered contained, including the Egley fires near Burns in Central Oregon, which have been burning since July 6 and scorched 140,000 acres.