LOS ANGELES — A major wildfire burning in Los Angeles and fueled by high winds swelled in size Friday as more than 1,000 firefighters worked to try to contain the blaze and prevent it from destroying any more homes.

Around 100,000 people were under evacuation orders after the so-called Saddleridge Fire broke out around 9 p.m. Thursday in the Los Angeles community of Sylmar in the San Fernando Valley.

By Friday evening, it had grown to more than 7,500 acres, was 13 percent contained and had damaged or destroyed at least 31 structures. More than a dozen were declared a total loss, the Los Angeles Fire Department said.

No deaths have been directly blamed on fire, but a man suffered cardiac arrest Thursday night in Porter Ranch, which was placed under a mandatory evacuation order, and was pronounced dead at a hospital, Mayor Eric Garcetti said.

"There are men and women who are sweating it out on the fire line, men and women who are wearing uniforms and badges protecting our homes, our families, our city,” Garcetti said at a news conference Friday in which he praised firefighters and police. "And we are so deeply grateful for these angels in this city of angels, and the work that they have done.”

The blaze was fueled by winds gusting around 50 mph and extremely low humidity of around 4 percent, Garcetti said. It was one of two large wildfires that broke out Thursday in Southern California amid Santa Ana winds.

The other fire, the so-called Sandalwood Fire in Riverside County, roared through a mobile home park in Calimesa. At least 74 structures have been destroyed and 16 were damaged. The fire is blamed in one death, officials said.

The Sandalwood Fire had burned 823 acres and was 10 percent contained as of Friday afternoon, fire officials said. Officials have said it was caused when material in a trash truck ignited and the load was dumped and the fire spread into vegetation.

California Gov. Gavin Newsom on Friday declared a state of emergency for Los Angeles and Riverside counties due to the fires, and he said that the state secured a fire management assistance grant from the Federal Emergency Management Agency, which among other things will allow local agencies to recover some costs. Garcetti also said he signed an emergency declaration for the Saddleridge Fire.

The cause of the Saddleridge Fire has not been determined, but Los Angeles Fire Chief Ralph Terrazas said that he was aware of a media report of a witness seeing fire fall from an electric transmission tower.

"Our arson investigators have interviewed we believe that witness, but certainly someone else who said something similar,” Terrazas said. “We are following all leads, and we still don’t have a determination.”

Red flag warnings in parts of the Los Angeles area, including in the San Fernando Valley were extended until 6 p.m. Saturday, the National Weather Service said, although it tweeted that winds were starting to slow Friday evening.

"An ember — it only takes one ember — can start another fire," Terrazas said, adding that "embers at this fire have traveled downwind over a mile."

High winds and elevated risk of wildfires across the state prompted utility companies to pre-emptively shut down power to prevent wildfires caused by power lines, including to around 2 million people in Northern California by Pacific Gas & Electric.

Southern California Edison also shut down power to around 13,000 customers, but in its statement said the Sylmar area was under a list of areas that was only under consideration for such a shutdown.

A spokesperson for the utility said that some of the Sylmar area is covered by SCE, but another part is covered by the Los Angeles Department of Water and Power. The LADWP said this week that it does not conduct public safety shutoffs before or during wind events, saying that its coverage area is highly urbanized and faces less wildfire risks.

"Determining the cause and origin of the fire is a lengthy process. Our priority right now is ensuring the safety of our customers, employees and first responders," Southern California Edison said Friday in a statement.

In Northern California, Pacific Gas and Electric said in a statement Friday that power had been restored to nearly all of the 738,000 customers who had been without because of the safety precaution shutdown.

PG&E officials said that its target is to reach 98 percent restored by Friday night.

In Los Angeles, residents in the fire zone praised firefighters.

"I'm just grateful for them. They saved my grandma's house up there,” Vetea Mahony said after he brought donuts to fire crews continuing to work in the neighborhood Friday. “The side of it, it got on fire, but thanks to them, you know, we're OK."

Kiran Gaur, whose home was also saved, said that she believed firefighters were doing God's work.

"I hugged them. I said, 'thank God' because it's not easy to build a house, right, so it's very emotional for me. It's a miracle, you know. God saved our house,” she said. "God never comes by himself. He always sends somebody, so those were the angels," she added.

Gaur said she and her family had been sleeping but fled when they woke up and saw nearby trees ablaze. Her friends were not so lucky and they lost their home in the fire, and a neighbor also had his home damaged by the blaze.