Thousands of firefighters battling California's Park Fire, other western blazes

Fire crews in Northern California are racing to contain the so-called Park Fire , near Chico, that has scorched more than 560 square miles, darkening the sky with smoke and haze.

The sprawling blaze — which officials say was sparked after a man pushed a burning car into a gully and then fled — was only 12% contained as of Sunday night. It had destroyed at least 100 structures, with about 4,200 more threatened.

"Unfortunately, that number will probably go up," Jay Tracy, a spokesperson at the Park Fire headquarters, told The Associated Press on Sunday. "Each day that number has potential to grow — our teams obviously don't do damage inspections when there is active fire in an area."

Cooler temperatures and increased humidity could help crews battle the fire, which is now the largest active wildfire in the nation and seventh largest in California's history.

The fire is contributing to poor air quality in a large swath of the northwestern U.S. and western Canada.

The Park Fire has drawn comparison to the 2018 Camp Fire that tore through the nearby community of Paradise, killing 85 people and torching 11,000 homes. Paradise and several other Butte County communities were under an evacuation warning Sunday.

• Wildfire Watch: Maps and data on fires raging in western U.S.

However, Cal Fire operations section chief Jeremy Pierce had some good news for the area, saying around midday that the Park Fire's southernmost front, which is closest to Paradise, was "looking really good," with crews focusing on mopping up the area over the next three days. He also said they don't expect it to move farther into Chico, a city of about 100,000 people just west of Paradise.

First responders initially focused on saving lives and property endangered by the Park Fire, but that has shifted to confronting the blaze head-on, Tracy said. Nearlry 4,000 firefighters are battling the blaze , aided by numerous helicopters and air tankers, and Tracy said reinforcements would give much-needed rest to local firefighters, some of whom have been working nonstop since the fire started Wednesday.

"This fire is surprising a lot of people with its explosive growth," he said. "It is kind of unparalleled."

The Park Fire was sparked on Wednesday. A Chico man accused of setting the fire was arrested Thursday and is due in court Monday.

The northern half of the fire still posed a challenge on Sunday, Pierce said, with crews using bulldozers and other equipment to build fire lines across rocky, difficult terrain and to try to stop the flames from spreading.

The Park Fire was one of more than 100 blazes burning in the U.S. on Sunday, according to the National Interagency Fire Center. Some were sparked by the weather, with climate change increasing the frequency of lightning strikes as the Western U.S. endures blistering heat and bone-dry conditions.

Despite the improved fire weather in Northern California, conditions remained ripe for even more blazes to ignite, with the National Weather Service warning of "red flag" conditions on Sunday across wide swaths of Utah, Colorado and Wyoming, in addition to parts of California.

In Southern California, a fire in the Sequoia National Forest swept through the community of Havilah after burning more than 48 square miles in less than three days. The town of roughly 250 people had been under an evacuation order.

Fires were also burning across eastern Oregon and eastern Idaho, where officials were assessing damage from a group of blazes referred to as the Gwen Fire, which was estimated at 43 square miles as of Sunday.