Support for crews fighting US wildfire

Out-of-state crews have headed to Montana to battle a blaze that injured five firefighters as the U.S. west struggles with a series of fires that have ravaged rural lands and destroyed homes.

Progress was made on the nation's largest blaze, the Bootleg Fire in Oregon, but less than half of it was contained on Saturday, fire officials said.

The growth of the sprawling fire has slowed, but increased fire activity was expected, and thousands of homes remained threatened on its eastern side.

"This fire is resistant to stopping at dozer lines," Jim Hanson, fire behaviour analyst, said in a news release from the Oregon Department of Forestry.

"With the critically dry weather and fuels we are experiencing, firefighters are having to constantly reevaluate their control lines and look for contingency options."

In California, Governor Gavin Newsom on Friday 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".

On Saturday, fire crews from California and Utah were headed to Montana, Governor Greg Gianforte said.

Five firefighters were injured on Thursday when swirling winds blew flames back on them as they worked on the Devil's Creek fire burning in rough, steep terrain near the rural town of Jordan.

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 July 4 in Alpine County, has destroyed at least 10 buildings.

In Butte County, California, the Dixie Fire continued to burn in rugged and remote terrain, hampering firefighters' efforts to contain the blaze as it grows eastward, becoming the state's largest wildfire this year.

In north-central Washington, firefighters battled two blazes in Okanogan County that threatened hundreds of homes.

And in northern Idaho, a small fire near the Silverwood Theme Park prompted evacuations. The theme park was back open on Saturday, with the fire half-contained.

Although hot weather with afternoon winds posed a continued threat of spreading blazes, weekend forecasts also called for a chance of scattered thunderstorms in California, Utah, Nevada, Arizona and other states.

More than 85 large wildfires were burning around the US, most of them in Western states, and they had burned more than 550,000 hectares.