Firefighters from the California Department of Forestry and Fire Protection’s Placerville station battle the Sugar Fire, part of the Beckwourth Complex, in Doyle on Friday.Noah Berger / AP

By Phil Helsel

Thousands of firefighters across 12 states are battling wildfires that have burned a total of more than 850,000 acres as extreme heat waves continue to scorch the West, officials said Tuesday.

More than 12,000 firefighters were deployed to put out nearly 60 large fires tearing across the country, according to the National Interagency Fire Center. Of the 12 states, Idaho, Arizona, Montana and California accounted for a large majority of the wildfires.

Wildfires blazed from as north as Alaska to as far midwest as Minnesota, the center said. Among the other states reporting active fires were Wyoming, Washington, New Mexico, Colorado and Utah.

The Beckwourth Complex, the largest wildfire burning in California, has burned more than 91,200 acres. It was 26 percent contained by Monday evening, up from 8 percent Sunday, fire officials said.

The fire complex was sparked by lightning in Plumas National Forest in Northern California, near the Nevada border, officials said. Around 20 homes were destroyed in the small town of Doyle, the fire department has said.

There were extreme fire conditions, California Incident Management Operations Section Chief Jake Cagle said. The “probability of ignition” is 100 percent, which means any ember or match in a fuel bed will cause a fire, he said.

“That’s the kind of extreme weather conditions we’re dealing with,” Cagle said in a video briefing Monday. “And it’s still early. This is stuff that we expect in August, for the past five, six, seven years — now we’re seeing it earlier in July.”

In southern Oregon, the Bootleg Fire had grown by around 5,000 acres by Monday morning, an improvement over the doubling in size that the fire had seen in recent days.

As of Tuesday morning, the fire was estimated at more than 200,000 acres, or about 312.5 square miles. It is burning in Fremont-Winema National Forest and started last Tuesday afternoon. A cause has not been determined.

Fire officials said a smoke inversion allowed firefighters to build and strengthen fire control lines Sunday. The fire has destroyed seven homes, a spokesman for the Oregon fire marshal said.

And in Arizona, two firefighters were killed in a plane crash while conducting aerial reconnaissance over the Cedar Basin Fire near Prescott National Forest, the Bureau of Land Management said in a statement.

Much of the Western U.S. has been dealing with extreme heat that has set or matched temperature records.

The heat wave has peaked for most areas, but excessive heat warnings will remain in place through Tuesday evening, the National Weather Service said.

California is coming off what fire officials said was one of the state’s worst years for wildfires. It included four of the five largest wildfires in California history, according to the California Department of Forestry and Fire Protection.

The state’s fifth-most destructive wildfire, the North Complex, which killed 15 people and destroyed more than 2,300 homes and other structures, also occurred last year.

Oregon also had a wildfire season that the governor said was unlike any other in recent memory. More than 1 million acres burned, more than 5,000 homes and commercial structures were destroyed, and nine people died, a government report released in January said.