‘Explosive’ California wildfire near Yosemite National Park burns more than 6,000 acres within hours

Oak Park fire marks third wildfire in Mariposa County in recent weeks as firefighters struggle to combat challenging blaze

An “explosive” and fast-moving California wildfire has challenged firefighters combatting a blaze that has grown to more than 10 square miles (26.5 kilometers) since it sparked on Friday afternoon, burning more than 6,500 acres and forcing evacuations near Yosemite National Park.

An update from the California Department of Forestry and Fire Protection on Saturday describes the Oak Fire as “extreme with frequent runs, spot fires and group torching” as the blaze reaches the Sierra National Forest.

“Emergency personnel are working to safely evacuate people and are actively engaged in protecting structures. Explosive fire behavior is challenging firefighters,” according to Cal Fire.

The fire – the largest among the state’s active wildfires – destroyed at least 10 residential and commercial structures and damaged at least five others as of Saturday morning. More than 6,555 acres burned by Saturday morning, with more than 400 fire personnel, 45 fire engines and four helicopters deployed to battle the blaze.

Several road closures include a portion of Highway 140, partially blocking access to Yosemite National Park.

The fire began Friday in the foothills of the Sierra Nevada near Midpines, roughly nine miles northeast from Mariposa, the seat of Mariposa County.

It marks the third wildfire in the county in two weeks.

It is unclear what sparked the fire. Fire officials have reported that a combustible combination of intense heat, dry vegetation and intense drought have fuelled wildfire blazes that are difficult to get under control.

An aerial view of the Oak Fire near Yosemite National Park shows smoke from the blaze above Yosemite Valley, California. (via REUTERS)

The state’s second-largest active wildfire, the Washburn Fire, has burned near the southern point of Yosemite for more than two weeks, burning nearly 5,000 acres, though officials report that it is 79 per cent contained.

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.

That fire broke out on 7 July near Yosemite and forced the closure of the park’s southern entrance and the evacuation of the town of Wawona as it threatened hundreds of giant sequoias.