A Northern California wildfire quickly swept through more than six square miles of drought-stricken land Saturday, threatening at least 150 rural homes in the Sierra Nevada, authorities said.

The blaze started around 2:30 p.m. and forced evacuations of some communities in and near Nevada County, about 45 miles northeast of Sacramento.

Firefighters aided by air tankers fought the blaze. It was in a rugged creek drainage area that fire engines couldn’t reach so crews were hiking in or being airlifted to the area, state fie spokeswoman Lynne Tolmachoff said.

The fire was jumping from tree to tree, turning them into torches and throwing embers a half-mile ahead, she said.

No injuries were reported.

The cause of the fire hasn’t been determined, but investigators are asking the public for help finding a white Jeep Wrangler with a roll bar and no front doors that was seen in the area around the time the fire started.

In Napa Valley wine country, firefighters gained ground Saturday against a wildfire there. Fire officials ended all evacuation orders and road closures.

Crews battling a separate blaze in Sierra Nevada on Friday have reopened one lane of freeway linking Sacramento and Reno and were escorting traffic through the fire area.

The Napa-area blaze has burned more than 10 1/2 square miles of drought-parched countryside near Lake Berryessa, about 45 miles east of wine country. Residents who evacuated about 50 homes when the fire broke out Wednesday were allowed to return by Friday.

All mandatory evacuations and road closures were lifted Saturday morning, Cal Fire said.

The blaze was 55 percent contained.

Businesses close to the wildfires say commerce hasn't been affected, with customers buying wine and renting cabins and boats by Lake Berryessa, one of California's largest bodies of fresh water.

"You're getting the last few weeks before school starts and getting all the fun you can," said Terry Sparkman, general manager of Pleasure Cove Resort & Marina, which is a few miles west of the wildfires.

The other fire, in the Sierra Nevada southwest of Lake Tahoe, has charred 200 acres of heavy timber. It was 75 percent contained Saturday.

It was burning about 60 miles east of Sacramento on both sides of the American River and U.S. Highway 50.

The Associated Press contributed to this report.