Authorities have redoubled efforts to find more victims of the deadliest wildfire in California history and to account for nearly 1000 people listed as missing, with forecast rains expected to hinder the search and raise the risk of mudslides.

Remains of 79 victims have been recovered since the Camp Fire erupted on November 8 and largely obliterated the Sierra foothills hamlet of Paradise, a town of nearly 27,000 people 280km north of San Francisco.

The latest official death toll was announced as the Butte County Sheriff's Office also said it was reducing the number of names on its missing persons list to 993, down from 1276 a day earlier.

The roster has fluctuated dramatically over the past week as additional individuals were reported missing, or as some initially listed as unaccounted for either turn up alive or end up being 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 had torched 61,107 hectares of drought-parched scrub and trees, incinerating more than 9800 homes along the way, the California Department of Forestry and Fire Protection (Cal Fire) said.

But firefighters in recent days have gained significant ground against the blaze, carving containment lines around two-thirds of its perimeter, Cal Fire said.

Efforts to further suppress the flames were likely to benefit from a storm expected to dump as much as 10cm of rain north of San Francisco, said Patrick Burke, a National Weather Service forecaster.

But heavy showers carry the potential for unleashing dangerous mudslides in newly burned areas while also making it more difficult for forensic teams sifting through cinders and debris in search of additional bodies.