By MARCIO SANCHEZ and CHRISTOPHER WEBER

OAK GLEN, Calif. (AP) — Rescuers searched Wednesday for a person missing in a mudslide that swept boulders down fire-scarred slopes in Southern California mountain communities, while firefighters held back a week-old blaze that gained renewed strength and forced more evacuations along foothills in the northern part of the state.

Workers with the Yucaipa Valley Water District work on repairing a reservoir used as a drinking source in the aftermath of a mudslide, Tuesday, Sept. 13, 2022, in Oak Glen, Calif. (AP Photo/Marcio Jose Sanchez)

With thunderstorms forecast and more mudslides possible, evacuation orders remained in place in parts of the San Bernardino Mountains where flash floods washed away cars and buried buildings late Monday east of Los Angeles.

Five hundred miles (805 kilometers) to the north, the Mosquito Fire destroyed structures when flames erupted Tuesday afternoon, just hours after officials had reported making “great strides” in the battle.

“The fire was held in check overnight” and crews were able to keep flames from entering the town of Foresthill, fire spokesperson Scott McLean said Wednesday. He said some buildings burned, but the exact number won’t be known until damage assessment teams were able to canvas the area 110 miles (177 kilometers) northeast of San Francisco.

The blaze was one of three large fires in the state.

In Southern California, crews searched street by street for people who might be trapped by

the mudflows that washed rocks, trees and other debris with astonishing force into Forest Falls, Oak Glen and Yucaipa and left a muddy mess and untold destruction.

Homes and other buildings were damaged, including a commercial building buried so high its roof collapsed, said Eric Sherwin, spokesperson for the San Bernardino County Fire Department.

“We have boulders that moved through that weigh multiple tons,” Sherwin said. “It could take days just to find all the cars that are missing because they are completely covered by mud.”

video showed a slow-moving black river of sludge rolling past the sign for the Oak Glen Steakhouse and Saloon on Monday followed seconds later by a surging wave of deeper mud carrying logs. The mud appeared to be head-high in places the next day.

Sherwin said crews were searching for one missing person.

Residents who tried to return home found it tough going in the sticky mess.

“I’ve never seen anything like this before,” said Perla Halbert, whose feet were caked in

The feet of Perla Halbert are covered in mud after she unsuccessfully tried to reach her property in the aftermath of a mudslide Tuesday, Sept. 13, 2022, in Oak Glen, Calif. Cleanup efforts and damage assessments are underway east of Los Angeles after heavy rains unleashed mudslides in a mountain area scorched by a wildfire two years ago. (AP Photo/Marcio Jose Sanchez)

mud after trying to walk to her home. “If you try and take two steps, you get submerged. You just get stuck.”

Halbert had been out of town and returned to her Oak Glen home late Monday to find the driveway covered with a few inches of mud. Her family stayed the night with family members and returned after first light to discover several feet of mud and a fence washed away.

Her husband went to buy boots and coveralls before trekking through the muck to assess the damage.

“There’s lots of rocks and so much mud. But hopefully the house itself is OK,” she said.

Officials lifted some mandatory evacuation and shelter in place orders Tuesday evening.

Workers were able to clear most of Valley of the Falls Drive — the only road to Forests Falls — and teams were assessing damage. Other major roads in the San Bernardino Mountains were reopened.

The rains were the remnants of a tropical storm that brought high winds and some badly needed rainfall to drought-stricken Southern California last week, helping firefighters largely corral the Fairview Fire that had been burning out of control about 20 miles (32 kilometers) south of the mudslides.

The mud flows and flash flooding occurred in parts of the San Bernardino Mountains where there are burn scars — areas where there’s little vegetation to hold the soil — from the 2020 wildfires.

The mudslides occurred about 175 miles (280 kilometers) east of Montecito, where enormous debris flows killed more than 20 people and destroyed hundreds of homes in January 2018, a month after a huge wildfire scorched hillsides.

The Fairview Fire was burning about 75 miles (121 kilometers) southeast of Los Angeles. The 44-square-mile (114-square-kilometer) blaze was 69% contained by Wednesday morning. Two people died fleeing the fire, which destroyed at least 35 homes and other structures in Riverside County.

The Mosquito Fire had grown to nearly 91 square miles (nearly 236 square kilometers),

with 20% containment Wednesday, according to the California Department of Forestry and Fire Protection, or Cal Fire.

Perla Halbert walks through the mud along her driveway in the aftermath of a mudslide Tuesday, Sept. 13, 2022, in Oak Glen, Calif. Cleanup efforts and damage assessments are underway east of Los Angeles after heavy rains unleashed mudslides in a mountain area scorched by a wildfire two years ago. (AP Photo/Marcio Jose Sanchez)

More than 11,000 people have been evacuated and nearly 6,000 structures are threatened — an increase in both figures as the blaze raged Tuesday near Foresthill and Todd Valley after a spot fire jumped the Middle Fork of the American River, officials said. More than 45 homes and other buildings have been destroyed.

Increased winds Tuesday pushed out a smoke inversion layer that had been stifling the blaze and gave fresh oxygen to the flames, McLean said. The area is full of extremely dry fuels that were rapidly igniting, challenging both firefighters on the ground and aircraft.

Scientists say climate change has made the West warmer and drier over the last three decades and will continue to make weather more extreme and wildfires more frequent and destructive. In the last five years, California has experienced the largest and most destructive fires in its history.

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Weber reported from Los Angeles. Associated Press writer Stefanie Dazio in Los Angeles contributed to this report.