The largest wildfire in the U.S. swelled to nearly 600 square miles this morning, bigger than the city of Los Angeles, fire officials in California said, as thousands of firefighters battled the blaze in a wilderness area north of Sacramento.

More than 5,000 firefighters from across California and other states were working around the clock to douse the Park Fire, burning in the state’s Central Valley, about 90 miles north of Sacramento, the capital. The fire grew to 383,600 acres, becoming the fifth-largest wildfire in Californian history, officials said.

The Park Fire today surpassed the size of the 2020 Creek Fire in Fresno County, which burned almost 380,000 acres, fire officials said. But it is still smaller than the state’s largest fire on record, the August Complex fire of 2020, which burned more than 1 million acres in seven counties in northern California.

The Park Fire – fueled by dry grass, brush and timber – is fast-moving, said Fire Capt. Dan Collins of the California Department of Forestry and Fire Protection or Cal Fire.

“This fire has lots of fuel that is receptive to burning, and it’s hard to get to,” he said. “Our fire line is 260 miles around, that’s the size of three Lake Tahoes. It can take two-three hours to get personnel in there over the terrain.”

The weather brings only a slight chance of a stray thunderstorm today, said Ashton Robinson Cook, a meteorologist with the National Weather Service. After that, no rain is in sight, and hot and extremely dry will prevail, he said.

Temperatures will reach 100 degrees Fahrenheit (37.8°C) on Wednesday and highs could hover at that level until next Monday, he said, with relative humidity dropping to as low as 7%.

The Park Fire, which was only 14% contained today, has forced the evacuation of more than 4,000 people and destroyed or damaged more than 192 structures, fire officials said. No injuries or deaths were reported.

Jeremy Hollingshead, a spokesman for Cal Fire, said that lingering clouds of smoke have grounded the 41 helicopters used to drop water and fire retarding chemicals on the blaze.

Evacuations included Paradise, the town that was devastated by the 2018 Camp Fire, the deadliest in the state’s history.

The man charged with starting the Park Fire, allegedly by pushing a flaming car down a Butte County gully last Wednesday, was formally charged with arson on Monday, but awaits additional charges, officials said.

The man, Ronnie Dean Stout II, 42, of Chico, California, denied wrongdoing at an arraignment on Monday, said Butte County District Attorney Mike Ramsey at a news conference. It was unclear if Stout had an attorney.

Stout did not enter a plea but was denied bail. His arraignment was continued to Thursday, as more charges could be added, Ramsey said.