Firefighters significantly slowed the spread of a smoky wildfire churning through forest near Yosemite National Park that has thousands of residents of remote mountain communities still under evacuation orders on Monday.

Crews “made good headway” against the Oak Fire, according to a Sunday night incident report by the California Department of Forestry and Fire Protection, or Cal Fire. “Fire activity was not as extreme as it has been in previous days.”

More than 2,500 firefighters with aircraft support battled the blaze that erupted Friday southwest of the park near the town of Midpines in Mariposa County. Officials described “explosive fire behaviour” on Saturday as flames made runs through bone-dry vegetation caused by the worst drought in decades.

By Sunday night the blaze had consumed more than 63 square kilometres of forest land with no containment, Cal Fire said. The cause of the fire was under investigation.

WATCH | Wildfire near Yosemite park tears through bone-dry forest:

Wildfire rips through forest near California’s Yosemite National Park

An uncontrolled wildfire near California’s Yosemite National Park, in Mariposa County, is tearing through bone-dry forest, challenging firefighters and forcing thousands of people to flee.

Firefighters working in steep terrain on the ground protected homes as air tankers dropped retardant on 15-metre flames racing along ridgetops east of the tiny community of Jerseydale. Personnel face tough conditions that include steep terrain, sweltering temperatures and low humidity, Cal Fire said.

Light winds blew embers ahead into tree branches “and because it’s so dry, it’s easy for the spot fires to get established and that’s what fuels the growth,” said Cal Fire spokesperson Natasha Fouts.

Fire ‘moving very fast’

Evacuations were in place for more than 6,000 people living across a several-kilometre span of the sparsely populated area in the Sierra Nevada foothills, though a handful of residents defied the orders and stayed behind, said Adrienne Freeman with the U.S. Forest Service.

“We urge people to evacuate when told,” she said. “This fire is moving very fast.”

A Cal Fire firefighter uses a hose to mop up hot spots after the Oak Fire moved through the area near Jerseydale, Calif., on Monday. (Justin Sullivan/Getty Images)

Residents affected by the Oak Fire listen to updates from fire officials during a community meeting in Mariposa County on Sunday. (Noah Berger/The Associated Press)

Lynda Reynolds-Brown and her husband, Aubrey, awaited news about the fate of their home from an evacuation centre at an elementary school. They fled as ash rained down and the fire descended a hill toward their property.

“It just seemed like it was above our house and coming our way really quickly,” Reynolds-Brown told KCRA-TV.

Gov. Gavin Newsom proclaimed a state of emergency for Mariposa County due to the fire’s effects.

Flames destroyed at least 10 residential and commercial structures and damaged five others, Cal Fire said. Assessment teams were moving through mountain towns to check for additional damage, Fouts said.

Numerous roads were closed, including a stretch of State Route 140 that’s one of the main routes into Yosemite.

More than 2,000 without power

California has experienced increasingly larger and deadlier wildfires in recent years as climate change has made the West Coast much warmer and drier over the past 30 years.

Scientists have said weather will continue to be more extreme and wildfires more frequent, destructive and unpredictable.

Pacific Gas & Electric said on its website that more than 2,600 homes and businesses in the area had lost power as of Monday, and there was no indication when it would be restored.

“PG&E is unable to access the affected equipment,” the utility said as flames roared Friday.

A bird flies as a firefighting aircraft drops flame retardant on a hillside to control the Oak Fire as it burns near Darrah in Mariposa County on Sunday. (Carlos Barria/Reuters)

The Oak Fire was sparked as firefighters made progress against an earlier blaze, the Washburn Fire, that burned to the edge of a grove of giant sequoias in the southernmost part of Yosemite National Park.

The 19-square-kilometre fire was 87 per cent contained after burning for two weeks and moving into the Sierra National Forest.