INDIAN FALLS, USA (AP) — California’s largest wildfire merged with a smaller blaze and destroyed homes in remote areas, leaving limited access for firefighters as numerous other fires gained strength and threatened property across the western states.

The massive Dixie Fire, which started July 14, had already levelled over a dozen houses and other structures when it combined with the Fly Fire and tore through the tiny northern California community of Indian Falls after dark Saturday.

An updated damage estimate was not available Sunday, though fire officials said the blaze had charred nearly 298 square miles (772 square kilometres) of timber and brush in Plumas and Butte counties. It was 21 per cent contained.

Firefighters carrying hand tools were forced to hike through rugged terrain where engines can’t go said Rick Carhart, spokesman for the California Department of Forestry and Fire Protection.

“It has been burning in extremely steep canyons, some places where it is almost impossible for human beings to set foot on the ground to get in there,” he said. “It’s going to be a long haul.”

Still, crews made progress Saturday by proactively setting fires to rob the main blaze of fuels, Carhart said.

The fire prompted evacuation orders in several small mountain communities and along the west shore of Lake Almanor, a popular resort area. About 10,000 homes remained under threat, officials said.

Firefighters also reported progress against the nation’s largest wildfire, the Bootleg Fire in southern Oregon, containing 46 per cent of the blaze that had consumed nearly 640 square miles (1,657 square kilometres).

More than 2,200 firefighters battled the blaze, focusing Sunday on constructing containment lines at the northern and eastern edges in dense timber. Crews could get a break from rain and higher humidity predicted for this week, said Marcus Kauffman, spokesman for the Oregon Department of Forestry.

The lightning-caused fire has burned 67 homes, mainly cabins, and at least 2,000 houses were under evacuation orders.