WAWONA, Calif. (AP) — A fast-moving brush fire near Yosemite National Park exploded in size Saturday into one of California’s largest wildfires of the year, prompting evacuation orders for thousands of people and shutting off power to more than 2,000 homes and businesses.

The Oak Fire, which began Friday afternoon southwest of the park near Midpines in Mariposa County, grew to 10.2 square miles (26.5 square kilometers) by Saturday morning, according to the California Department of Forestry and Fire Protection, or Cal Fire. It erupted as firefighters made progress against an earlier blaze that burned to the edge of a grove of giant sequoias in the southernmost part of Yosemite park.

Evacuation orders were put in effect Saturday for over 6,000 people living in the sparsely populated, rural area, said Daniel Patterson, a spokesman for the Sierra National Forest.

“Explosive fire behavior is challenging firefighters,” Cal Fire said in a statement Saturday morning that described the Oak Fire’s activity as “extreme with frequent runs, spot fires and group torching.”

By Saturday morning, the fire had destroyed 10 residential and commercial structures, damaged five more and was threatening 2,000 more structures, Cal Fire said. The fast-growing blaze prompted numerous road closures, including a shutdown of Highway 140 between Carstens Road and Allred Road — blocking one of the main routes into Yosemite.

More than 400 firefighters, along with helicopters, other aircraft and bulldozers, battled the blaze, which was in a sparsely populated, mostly rural area of the Sierra Nevada foothills, said Daniel Patterson, a spokesman for the Sierra National Forest.

Hot weather, low humidity and bone dry vegetation caused by the worst drought in decades was fueling the blaze and challenging fire crews, Patterson said.

“The fire is moving quickly. This fire was throwing embers out in front of itself for up to 2 miles yesterday,” Patterson said. “These are exceptional fire conditions.”

Pacific Gas & Electric said on its website that more than 2,600 homes and businesses in the area had lost power as of Friday afternoon and there was no indication when it would be restored. “PG&E is unable to access the affected equipment,” the utility said.

A shoeless older man attempting to flee the blaze on Friday crashed his sedan into a ditch in a closed area and was helped by firefighters. He was safely driven from the area and did not appear to suffer any injuries. Several other residents stayed in their homes Friday night as the fire continued to burn nearby.

The cause of the fire was under investigation, Cal Fire said.

Meanwhile, firefighters have made significant progress against a wildfire that began in Yosemite National Park and burned into the Sierra National Forest.

The Washburn Fire was 79% contained Friday after burning about 7.5 square miles (19.4 square kilometers) of forest.

The fire broke out July 7 and forced the closure of the southern entrance to Yosemite and evacuation of the community of Wawona as it burned on the edge of Mariposa Grove, home to hundreds of giant sequoias, the world’s largest trees by volume.

Wawona Road is tentatively set to reopen on Saturday, according to the park website.

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