A Northern California wildfire that destroyed a foothill hamlet has become the state's deadliest blaze of the year with 10 people confirmed dead and the toll could climb as searchers look for 16 missing people. 

The North Complex fire that exploded in wind-drive flames earlier in the week was advancing more slowly Friday after the winds eased and smoke from the blaze shaded the area and lowered the temperature, allowing firefighters to make progress, authorities said.However, the smoke made for poor visibility and fire helicopters couldn't fly Thursday. 

In most parts of the state, red flag warnings of extreme fire danger because of hot, dry weather or gusty winds were lifted.

Only a day or two earlier, the North Complex fire tore through Sierra Nevada foothills so quickly that fire crews were nearly engulfed, locals fled for their lives to a pond, and the town of Berry Creek, population 525, was gutted.

On Thursday, Butte County sheriff's Capt. Derek Bell said seven bodies were discovered, bringing the total to 10 in two days. At least four people wjth critical burns were hospitalised.

Deputies and detectives were searching for human remains as they made their way into devastated areas with a team of anthropologists from Chico State University, Bell said.

Burned-out and overturned cars, downed power lines and the ruins of buildings littered Berry Creek and nearby areas, the Sacramento Bee reported.

One hatchback found on a dirt road had three dead dogs in it, while a pickup truck had the remnants of a guitar case and melted CDs in the bed. 

More than 2,000 homes and other buildings had burned in the fire, which began several weeks ago as a lightning-sparked collection of fires northeast of San Francisco. 

The final toll is expected to be much higher. Damage assessment teams planned to begin a methodical search of the burned areas on Friday.

Among those unaccounted for were Sandy Butler and her husband, who had called their son to say they were going to try to escape the flames by finding shelter in a pond.

We're still hoping and praying for good news, said Jessica Fallon, who has two children with the Butler's grandson and considers them her own grandparents.

Everything is replaceable, but not my grandparents' lives. I'd rather lose everything than those two. They kind of held the family together.

Fallon said she'd been peppering hospitals with phone calls in search of her grandparents. There was no word of them late Thursday night.

The speed and ferocity of the fire astonished observers, even those who remembered a blaze only two years earlier that killed some 85 people and devastated the town of Paradise, a few miles away from the current blaze.Residents jammed the main road out of town on Wednesday amid falling ash and red skies.Authorities lifted an evacuation warning for Paradise on Thursday but authorities urged people to remain alert.