An air tanker drops retardant as the Maria Fire approaches Santa Paula, Calif., on Friday, Nov. 1, 2019. According to Ventura County Fire Department, the blaze has scorched more than 8,000 acres and destroyed at least two structures. (AP Photo/Noah Berger)

LOS ANGELES (AP) — Crews fought a pitched battle against the last remaining large wildfire in Southern California as the stubborn flames threatened nearly 2,000 homes and other buildings.

The fire that erupted on a hilltop northeast of Los Angeles headed for what would be its third day Saturday and firefighters were finding it hard work as shifting winds made the front line a moving target.

The Maria Fire had burned some 15 square miles (38 square kilometers) and prompted evacuation orders for nearly 11,000 people since it began Thursday evening.

Eastern Ventura, Camarillo, Somis and Santa Paula were at risk, Ventura County fire officials said.

On Friday, a tug of war developed between onshore and offshore winds.

"It has been an uphill battle ever since," Ventura County Fire Chief Mark Lorenzen said. "As winds shift, we have a whole new fuel bed open up."

Winds and skin-cracking low humidity were expected to make Saturday another difficult day for firefighters.

Crews battled to keep the flames away from orchards and farms in the rural area. Three buildings were destroyed.

The cause was under investigation but there was a troubling possibility that an electrical line might have been involved — as such lines have been at other recent fires.

Southern California Edison said Friday that it re-energized a 16,000-volt power line 13 minutes before the fire erupted in the same area.

Edison and other utilities up and down the state shut off power to hundreds of thousands of people this week out of concerns that high winds could cause power lines to spark and start fires.

SCE will cooperate with investigators, the utility said.

The fire began during what had been expected to be the tail end of a siege of Santa Ana winds that fanned fires that destroyed buildings and prompted mass evacuations across the region.

The fires even caught the attention of teenage climate-change activist Greta Thunberg, who was visiting Los Angeles for a rally.

"It has been horrifying to see what is going on here and what happens here often and that it's gotten worse because of the climate crisis," she said.

Red flag weather warnings of extreme fire danger had been expected to expire Friday evening but forecasters extended them to 6 p.m. Saturday for valleys and interior mountains of Ventura and Los Angeles counties, citing the withering conditions.

In Northern California, more people were allowed to return to areas evacuated due to the huge Kincade Fire burning for days in the Sonoma County wine country.

The 121-square-mile (313-square-kilometer) fire was 70% contained, the California Department of Forestry and Fire Protection said.

The tally of destroyed homes reached 174 and there were 35 more damaged, Cal Fire said. Many other structures also burned.

Historic, dry winds prompted the state's largest utility, Pacific Gas & Electric Co., to initiate four rounds of widespread pre-emptive shut-offs in Northern California this month to prevent wildfires.

But the Contra Costa County Fire Protection District pegged the utility's equipment as the cause of three smaller fires that cropped up Sunday in the San Francisco Bay Area suburbs of Martinez and Lafayette.

And while the cause of the Kincade Fire hasn't been determined, PG&E reported a problem with a transmission tower near the spot where the fire started.

A firefighter creates a fire break as the Maria Fire approaches in Santa Paula, Calif., on Friday, Nov. 1, 2019. According to Ventura County Fire Department, the blaze has scorched more than 8,000 acres and destroyed at least two structures. (AP Photo/Noah Berger)
An inmate firefighter creates a fire break as the Maria Fire approaches in Santa Paula, Calif., on Friday, Nov. 1, 2019. According to Ventura County Fire Department, the blaze has scorched more than 8,000 acres and destroyed at least two structures. (AP Photo/Noah Berger)
Flames from a backfire consume a hillside as firefighters battle the Maria Fire in Santa Paula, Calif., on Friday, Nov. 1, 2019. According to Ventura County Fire Department, the blaze has scorched more than 8,000 acres and destroyed at least two structures. (AP Photo/Noah Berger)
Firefighter Giannis Giagos battles the Maria Fire in Santa Paula, Calif., on Friday, Nov. 1, 2019. According to Ventura County Fire Department, the blaze has scorched more than 8,000 acres and destroyed at least two structures. (AP Photo/Noah Berger)
A firefighter battles the Maria Fire Thursday, Oct. 31, 2019, in Somis, Calif. (AP Photo/Marcio Jose Sanchez)
Justo and Bernadette Laos show a photo of the home they rented that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. The fire started last week near the town of Geyserville in Sonoma County north of San Francisco. (AP Photo/Charlie Riedel)
A friend of Bernadette Laos displays jewelry salvaged from her home that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. The fire started last week near the town of Geyserville in Sonoma County north of San Francisco. (AP Photo/Charlie Riedel)
Bernadette Laos looks at jewelry she salvaged from her home that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. (AP Photo/Charlie Riedel)
Brenda Catelani stands in her garage and shows ember she found in her backyard in Windsor, Calif, Thursday, Oct. 31, 2019. She and her husband were evacuated for four nights as firefighters battled the Kincade Fire, which reached the edge of their neighborhood. The fire was the largest to burn over a three-week siege of gusty winds that fanned fast-moving wildfires across California and led utility companies to cut power to millions to prevent breezes from blowing branches into electric lines and igniting an inferno. (AP Photo/Terry Chea)
Bernadette Laos looks for salvageable items in her home that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. (AP Photo/Charlie Riedel)
Justo and Bernadette Laos hug while looking through the charred remains of the home they rented that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. The fire started last week near the town of Geyserville in Sonoma County north of San Francisco. (AP Photo/Charlie Riedel)
Bernadette Laos looks for salvageable items in her home that was destroyed by the Kincade Fire near Geyserville, Calif., Thursday, Oct. 31, 2019. (AP Photo/Charlie Riedel)
A destroyed bridge leads to a driveway of a property charred in the Kincade Fire near Healdsburg, Calif., Thursday, Oct. 31, 2019. (AP Photo/Charlie Riedel)
Firefighters battle the Maria Fire Friday, Nov. 1, 2019, in Somis, Calif. (AP Photo/Marcio Jose Sanchez)
A lone tree stands on a hill charred in the Kincade Fire near Healdsburg, Calif., Thursday, Oct. 31, 2019. (AP Photo/Charlie Riedel)
Meat department employees Jessica Powers and Brian Sullivan place spoiled meat in a dumpster behind Big John's Market in Healdsburg, Calif. as they help get the store ready to reopen Thursday, Oct. 31, 2019. Power was restored to the family-owned grocery store late Tuesday after being turned off for four days in an attempt to stem fires caused by wind-damaged power lines. Employees have been working since being allowed back into the town Wednesday to throw out spoiled stock and restock the store. (AP Photo/Charlie Riedel)
A firefighter sprays water on a leveled home as the Hillside Fire burns in San Bernardino, Calif., on Thursday, Oct. 31, 2019. Whipped by strong wind, the blaze destroyed multiple residences. (AP Photo/Noah Berger)
A firefighter stands on a road as the Maria Fire burns behind him Friday, Nov. 1, 2019, in Somis, Calif. (AP Photo/Marcio Jose Sanchez)
A charred lawn chair overlooks a valley filled with smoke from the Kincade Fire near Healdsburg, Calif., Nov. 1, 2019. (AP Photo/Charlie Riedel)
A firefighting helicopter flies over a valley filled with smoke from the Kincade Fire near Healdsburg, Calif., Nov. 1, 2019. (AP Photo/Charlie Riedel)
A charred lawn chair overlooks a valley filled with smoke from the Kincade Fire near Healdsburg, Calif., Nov. 1, 2019. (AP Photo/Charlie Riedel)