Firefighting crews made progress against the deadliest wildfire in California history amid concerns that the death toll of 56 would rise. Picture: AP Photo/Noah Berger, File

Paradise, California- Firefighting crews made progress against the deadliest wildfire in California history on Thursday amid concerns that the death toll of 56 would rise as search teams work their way through the burned-out town of Paradise in the state's north.

More than 9 000 personnel from many US states are fighting the Camp Fire, which incinerated Paradise, and the Woolsey Fire hundreds of miles to the south.

Authorities attributed the high number of casualties to the staggering speed with which the wind-driven flames blew through Paradise. Nearly 8 700 homes were destroyed and 15 500 buildings threatened, the California Department of Forestry and Fire Protection (Cal Fire) said on Thursday.

Cal Fire said that 40 percent of the Camp Fire had been contained, up from 35 percent, even as the blaze grew 2 000 acres to 140 000 acres (57 000 hectares).

Diminished winds and rising humidity helped firefighters shore up containment lines on Wednesday.

U.S. National Guard troops are in Paradise looking for remains of victims as 130 people, most over the age of 65, were still listed as missing.

Authorities fear that in the crush to flee the fast-approaching flames, some elderly residents may have been left behind. At least 22 cadaver dogs are part of the search.

Paradise's ghostly expanse of empty lots covered in ash and strewn with twisted wreckage and debris made a strong impression on Governor Jerry Brown, US Interior Secretary Ryan Zinke and other officials who toured the devastation on Wednesday and were due to visit the scene of the Woolsey Fire on Thursday.

Paradise, in the Sierra foothills about 175 miles (280 km) north of San Francisco, burned last Thursday and its 27 000 residents are unsure of what to do next. With 50 000 people still under evacuation orders, a Walmart that had been spared from the fire has become a haven for fire refugees.

A section of its parking lot was roped off for use as a distribution centre for clothes, food and coffee, while people who fled their homes set up dozens of tents in an adjacent field or slept in their cars in the parking lot. Portable toilets were brought in.

Evacuees milling in the parking lot were facing morning temperatures that dropped into the mid-30s and many wore breathing masks for protection from lingering smoke.

At another evacuation centre south of Paradise in Oroville, Nanette Benson, said her future is uncertain.

"We don't know where the hell we're going to go," she told KRCR TV.

LOOTING IN PARADISE

Paradise's police department stepped up patrols after arresting three people on charges of looting. The department is relying on equipment from other police departments and is running off a generator, Sergeant Steve Bertagna told KRCR TV.

Thirteen of the department's 30 officers have lost their homes, KRCR TV said.

The blaze, fueled by thick, drought-desiccated scrub, has capped two back-to-back catastrophic wildfire seasons in California that scientists largely ascribe to prolonged drought that is symptomatic of climate change.

The high winds have eased, Cal Fire Director Ken Pimlott told reporters late on Wednesday, but vegetation around the Camp Fire remained critically dry and conditions were dangerous.

Lawyers for some wildfire victims claimed in a lawsuit filed this week that lax equipment maintenance by an electric utility caused the fire, which officially remains under investigation.

The Butte County disaster coincided with blazes in Southern California, especially the Woolsey Fire, which has killed at least two people, destroyed more than 500 structures and displaced 200 000 people west of Los Angeles.

Cal Fire said the Woolsey Fire was about 57 percent contained on Wednesday, up from 52 percent. Crews battling the fire were hoping for a help from the weather on Thursday with light onshore winds expected to bring slightly cooler temperatures and higher humidity levels.

The Camp Fire also stands as one of the deadliest U.S. wildfires since the turn of the last century. More than 80 people perished in the Big Burn firestorm that swept the northern Rockies in August 1910, consuming 3 million acres.

Reuters