By Jonathan Allen and Nick Carey

(Reuters) – Heavy rains are expected in northern California on Tuesday, raising the risk of mudslides and hindering the search for more victims of the deadliest wildfire in the state’s history as nearly 1,000 people remain listed as missing.

Remains of 79 victims have been recovered since the Camp Fire erupted on Nov. 8 and largely obliterated the Sierra foothills town of Paradise, a community of nearly 27,000 people about 175 miles (280 km) north of San Francisco.

The missing persons list kept by the Butte County Sheriff’s Office still has 993 names on it. That number has fluctuated dramatically over the past week as additional people were reported missing, or as some initially listed as unaccounted for either turn up alive or are identified among the dead.

Sheriff Kory Honea has said some people have been added to the list more than once at times under variant spellings of their names.

As of Monday, the fire has torched more than 151,000 acres (61,100 hectares) of parched scrub and trees, incinerating about 12,000 homes along the way, Cal Fire said.

Containment lines have been built around 70 percent of its perimeter, according to the agency.

Efforts to further suppress the flames were likely to benefit from a storm expected to dump as much as 4 inches (10 cm) of rain north of San Francisco between late Tuesday and Friday, said Patrick Burke, a National Weather Service forecaster.

‘MUDDY, MUSHY MESS’

But heavy showers risk setting off mudslides in newly burned areas while also making it more difficult for forensic teams sifting through cinders and debris for additional human remains.

Colleen Fitzpatrick, founder of the California-based consulting company Identifinders International, said rain would turn the site into a “muddy, mushy mess”, slick with wet ash.

Pathologists from the University of Nevada, Reno worked through the weekend as firefighters peeled back debris, collecting bits of burned bones and photographing everything that might help identify victims.

The risk of mudslides could also increase the misery of the evacuees, some of whom are living in tents or camping out of their cars. Residents who only recently were permitted back in homes that survived the fire may be ordered to evacuate again if they live downslope from badly burned areas.

Intense fire over the slopes of canyons, hills and mountains makes them more prone to landslides, by burning away vegetation and organic material that normally holds soil in place. The fire also creates a hard, waxy surface that tends to repel rather than absorb water.

The result can be a heavy runoff of rainwater mixed with mud, boulders, trees and other debris that flows downhill with tremendous force, said Jason Kean, a research hydrologist for the U.S. Geological Survey.

“Those debris flows have the consistency of wet concrete and move faster than you can run,” he said. “It’s like a flood on steroids … and a big one can take out two-story buildings.”

The number of residents needing temporary shelter was unclear, but as many as 52,000 people were under evacuation orders at the height of the firestorm last week.

Nearly 500 miles south of Paradise near Malibu, west of Los Angeles, at least two inches of rain are expected to fall on a second fire, the Woolsey, which has killed three people. That blaze was 94 percent contained by Monday morning.

The cause of both fires is under investigation, but electric utilities reported localized equipment problems around the time they broke out.

PG&E has said it could face liability that exceeds its insurance coverage if its equipment were found to have caused the Camp Fire.

(Reporting by Brendan O’Brien in Milwaukee; editing by David Stamp)