A jet aerial tanker drops its load of fire retardant on a fire near Pollack Pines. Picture: Rich Pedroncelli

Sacramento - A major wildfire burning north-east of Sacramento has charred more than 170 hectares and destroyed five homes, California fire officials said on Thursday.

The blaze, which started as five separate fires along Interstate 80 near the community of Applegate on Wednesday, prompted evacuations and the closure of all but one lane of I-80 eastbound, the California Department of Forestry and Fire Protection (Cal Fire) said on its website.

The fire threatened about 1 000 homes and was 20 percent contained on Thursday morning, the agency said, and a smoky haze hung over the state capital 65km away.

Winds on Wednesday moved the blaze toward the south-east, raising concerns that it could engulf the nearby American River Canyon, where brush and timber are “tinder dry” because of California's prolonged drought, Cal Fire spokesman Daniel Berlant said.

“We are hoping we don't see the same wind we saw yesterday,” Berlant said. Dry weather and warmer temperatures are expected to continue, however, Berlant said.

About 1 200 personnel were dispatched to fight the fire with 128 engines, seven helicopters and 18 bulldozers.

As its air tankers were grounded after a crash on Tuesday that killed a pilot who had been fighting the so-called Dog Rock Fire in Yosemite National Park, Cal Fire has been using planes borrowed from the federal government to fight the Applegate fire, Berlant said.

“That's what we used yesterday and today - the federal contract tankers,” Berlant said. “We're lucky that there's not so much fire activity going on around the country right now.”

The state has contracts with the US Forest Service to share air tankers as needed to fight fires, Berlant said.

The National Park Service said on Thursday that investigators had determined that the Dog Rock Fire was started by sparks from a vehicle, possibly safety chains dragging on pavement or brakes.

The blaze had blackened 99 hectares near the entrance of Yosemite by Thursday afternoon and was only 10 percent contained, according to a multi-agency fire tracking website.

A Yosemite spokeswoman said evacuation orders had been lifted for the foothill community of Foresta. - Reuters