Wildfire in Calimesa, California, races through mobile home park

LOS ANGELES — A rapidly growing wildfire fire destroyed numerous structures and injured an unknown number of people at a mobile home park east of Los Angeles on Thursday as power companies began expanding fire-prevention blackouts to the southern part of the state.

Riverside County fire officials said mandatory evacuations had been ordered at and around the Villa Calimesa Mobile Home Park in Calimesa, about 70 miles east of Los Angeles.

The Sandalwood Fire, which was first reported at about 2 p.m. and more than tripled in size to about 500 acres in less than a half-hour, destroyed multiple structures and caused “numerous medical emergencies,” the Riverside County Fire Department said.

The agency said the fire, which was at 0 percent containment, was caused by a trash truck that dumped a load of burning trash that spread into vegetation. Authorities said they had no further immediate information.

The mobile home park, which was built in 1958, has 110 manufactured housing sites, nearly all of which are occupied, according to the website of the park’s parent company.

The fire came as so-called Santa Ana winds, which blow down from mountains in the northern part of the state into the south, began gusting strongly Thursday afternoon.

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Power utilities had already instituted rolling power blackouts for about 2 million people in Northern California to prevent faulty power lines from sparking wildfires amid strong winds and low humidity.

Forecasters had predicted strong winds in the north would create Santa Ana conditions in the south on Wednesday and Thursday. Southern California Edison said Wednesday it had begun shutting off power to more than 30,000 people across its service area.

Fire officials said the Calimesa fire was threatening high-tension power lines. SCE said that it hadn’t cut off power to Calimesa but that parts of the community were in an area where such blackouts might be necessary this week.

In Northern California, Pacific Gas & Electric said Thursday afternoon that it had begun restoring power to about 126,000 accounts.

An account can be a single-family home or a large business, and generally represents about 2½ people. PG&E said about 600,000 accounts remained without power Thursday, which would represent about 1.5 million people.

PG&E has said it could be several days before all power is restored because all 24,700 miles of distribution lines and 2,443 miles of transmission line must be visually inspected before it can turn the power back on — a process that can’t get widely underway until the threatening fire conditions have passed.

Many Californians, including Gov. Gavin Newsom, have harshly criticized PG&E for the blackouts.

“They’re in bankruptcy because of their terrible management going back decades,” Newsom said Wednesday. “They created these conditions.”

PG&E’s energy unit declared the largest utility bankruptcy in U.S. history in January as it faced massive liabilities from its role in several highly destructive fires that burned hundreds of thousands of acres of Northern California in 2017 and 2018. One of them, the Camp Fire, killed 86 people in Butte County.

The governor doubled down on Thursday, calling the blackouts “unacceptable” at a news conference at the state emergency operations center in Mather.

“If they had de-energized this time last year and a year ago, a lot of people would be alive,” he said. “A lot of people’s lives were lost because they did not do the right thing.”

PG&E told NBC News this week that because the blackouts are a planned safety measure, customers wouldn’t be reimbursed for lost business, housing alternatives or spoiled food and medicines. Newsom said that he thought customers should be compensated and that he was in discussions with the company.

At PG&E’s daily update on Thursday evening, Chief Executive William Johnson declined to comment on Newsom’s remark, but he apologized for what he called the company’s failure to keep its customers in the loop.

Acknowledging that PG&E’s website had crashed for more than a day, that its phone lines were frequently jammed and that some blackout maps might have been inaccurate, Johnson said, “To put it simply, we were not adequately prepared to support the situational event.”

At the same time, he warned that because the goal was “zero spark,” similar blackouts are likely in the future under similar weather conditions. When they do, he said, “we’ve got to get more surgical.”