Monster wildfire in California rages on after killing two firefighters

A monster wildfire in northern California burned unchecked on Saturday after it killed two firefighters, destroyed hundreds of structures and sent thousands of frantic residents racing from their homes.

Some 3,400 firefighters on the ground and in helicopters and airplanes battled the 48,300-acre (19,500 hectares) Carr Fire early on Saturday as it ripped through Redding, a city of 90,000 people, in California's scenic Shasta-Trinity area.

More than 38,000 residents in Redding and elsewhere in Shasta County fled their homes as the fire began to gain speed and intensity on Thursday, destroying 500 structures and leaving Keswick, a town of 450, in smoldering ruins.

The fire, which was just three percent contained after igniting six days ago, has been fed by high temperatures and low humidity, which were expected for at least the next week, said California Department of Forestry and Fire Protection (CalFire) Director Ken Pimlott.

"This fire is a long way from done," he said.

A bulldozer operator and a member of the Redding Fire Department were killed in the blaze. A Redding hospital said it had treated eight people, including three firefighters.

The flames erupted into a firestorm on Thursday when it jumped across the Sacramento River and swept into the western side of Redding, about 240 km north of Sacramento, before gale-force winds during the night created a fire "tornado."

"This fire was whipped up into a whirlwind of activity, uprooting trees, moving vehicles, moving parts of roadways," Pimlott said.

Firefighters and police were hustling door to door to usher civilians out of harm's way, said Scott McLean, a spokesman for the California Department of Forestry and Fire Protection (CalFire).

California has had its worst start to the fire season in a decade, with 289,727 acres burned through Friday morning, according to National Interagency Fire Center (NIFC) data.

Governor Jerry Brown requested emergency federal assistance to prevent an "imminent catastrophe" as Shasta County tried to find supplies and water for evacuated residents and care for horses and cattle rescued from ranches and farms.

Wildfires have blackened an estimated 4.15 million acres (1.68 million hectares) in the United States this year. That was well above average for the same period over the past 10 years but down from 5.27 million acres (2.13 million hectares) in the first seven months of 2017, NIFC reported.

Cal Fire said the Cranston Fire, about 177 km east of Los Angeles had blackened 12,300 acres and was 16 percent contained. The Ferguson Fire near Yosemite, which has charred 46,675 acres, was 29 percent contained.