Flames racing through rugged terrain in Northern California destroyed multiple homes on Saturday as the state’s largest wildfire intensified and numerous other blazes battered the US West.

The Dixie fire, which started on July 14, had already levelled more than a dozen houses and other structures when it tore through the tiny town of Indian Falls after dark.

It was burning in a remote area with limited access, hampering firefighters’ efforts as it advanced eastward, fire officials said.

The blaze has charred more than 73,200 hectares (181,000 acres) in Plumas and Butte counties and prompted evacuation orders in several small communities and along the west shore of Lake Almanor, a popular getaway.

Meanwhile, the nation’s largest wildfire, southern Oregon’s Bootleg fire, was nearly halfway surrounded on Saturday as more than 2,200 crew members worked to corral it in the heat and wind, fire officials said.

The growth of the sprawling blaze had slowed, but thousands of homes remained threatened on its eastern side, officials added.

In California, Governor Gavin Newsom has declared a state of emergency for four northern counties because of wildfires that he said were causing “conditions of extreme peril to the safety of persons and property”.

Elsewhere in California, the Tamarack fire south of Lake Tahoe continued to burn through timber and chaparral and threatened communities on both sides of the California-Nevada state line. The fire, sparked by lightning on July 4 in Alpine County, has destroyed at least 10 buildings.

In north-central Washington state, firefighters battled two blazes in Okanogan County that threatened hundreds of homes and again caused hazardous air quality conditions Saturday.

And in northern Idaho, east of Spokane, a small fire near the Silverwood Theme Park prompted evacuations on Friday evening at the park and in the surrounding area. The theme park was back open on Saturday, with the fire half contained.

More than 85 large wildfires were burning around the country, most of them in western states, and they had burned more than 553,000 hectares (1.4 million acres).