An illegal cooking fire at an encampment near a Los Angeles freeway sparked a fast-moving wildfire last week that destroyed homes in the tony Bel-Air neighborhood and closed down a major freeway, authorities said Tuesday.

The Los Angeles Fire Department said that the cooking fire in a brush area near Sepulveda Boulevard where it passes underneath the 405 Freeway was the cause of the so-called Skirball Fire, which broke out at around 5 a.m. Wednesday and destroyed six homes.

There have been no arrests, the Fire Department said. The fire was at a homeless encampment, LAFD public information director Peter Sanders said.

The Skirball Fire forced the closure of the freeway, a major north-south artery in Los Angeles, and prompted worries that it could jump the freeway and threaten the Getty Museum and its priceless art collection.

The fire, which burned more than 400 acres, was 85 percent contained on Tuesday, the Fire Department said.

The fire broke out as firefighters across Southern California battles several other large wildfires, the largest of which, the Thomas fire in Ventura and Santa Barbara counties, was 25 percent contained as of Tuesday evening, according to the California Department of Forestry and Fire Protection, also known as Cal Fire.

One death has been blamed in all of the recent fires. A 70-year-old woman died in a car crash "during active fire evacuation" from the Thomas Fire, the Ventura County medical examiner said. The body of Virginia Pesola, of Santa Paula, was found on Wednesday.

A mansion that survived a wildfire sits on a hilltop in the Bel Air district of Los Angeles on Dec. 6, 2017. Jae C. Hong / AP

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The Thomas fire has destroyed nearly 800 homes or other structures since it broke out on Dec. 4, and still threatens 18,000 other structures, according to Cal Fire. The fire has burned more than 236,000 acres — more than 368 square miles — and thousands of people were ordered to leave their homes.

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Very dry conditions are expected to persist in the Thomas Fire area, National Weather Service meteorologist Rich Thompson said at a Tuesday evening news conference.

"When you look at the fire in the daylight hours, especially from the Santa Barbara front county perspective, the fire looks very benign," Tim Chavez, a Cal Fire fire behavior analyst, said.

Much of the acres being burned recently are when the fire moves at night, he said, which poses challenges to firefighting. Due to shifting winds, “that growth at night will continue for the next couple of days,” he said.

The cause of the Thomas Fire is still under investigation. So far the fire has destroyed 504 single-family homes in the city of Ventura, 196 in unincorporated Ventura County, and 5 in unincorporated Santa Barbara County, Cal Fire public information officer Bill Murphy said.

Several other large fires that were burning in Southern California have been largely contained. The Lilac fire in San Diego County, which killed horses and destroyed 151 homes or other structures since it broke out on Thursday, burned 4,100 acres and was 92 percent contained, according to Cal Fire.

The Creek Fire in Los Angeles County near the community of Sylmar was 98 percent contained, and the Rye Fire near Santa Clarita north of Los Angeles was 96 percent contained as of Tuesday afternoon, according to the U.S. Forest Service and Cal Fire.

A man sits in his car as he watches flames from the Thomas Fire in the hills of Montecito, California, Dec. 11, 2017. Robyn Beck / AFP - Getty Images

In the town of Summerland in Santa Barbara County, up the coast from Ventura, residents are under voluntary evacuation orders and some are staying, an employee at a local bar and restaurant said.

“It’s the worst I’ve ever seen it, and I just feel so bad because there’s so many displaced people,” Andrea Lionello, who works at The Nugget in Summerland, which is staying open, told NBC News on Tuesday.

She and her family are camping out at their in-laws. "But we're all in the same boat," Lionello said. "We just have to still keep plugging through and pushing through."