A fire burning near Big Bear in the San Bernardino National Forest continues to swell, forcing evacuations and confounding firefighters' efforts to contain it.

The blaze in the area of Jenks Lake in the Barton Flats was approximately 10,000 acres in size as of 8:15 p.m. on Thursday. It was burning timber and grass and prompted more than 150 people to be evacuated.

"When you have fires that burn in timber, the way this one's doing here, it creates its own weather," said Chon Bribiescas, with the U.S. Forest Service. "Because it's heavy timber ... there's a lot of heat. It kind of does what it wants to do"

It was reported just before 4 p.m. Wednesday, and is burning east of Camp de Benneville Pines south of Jenks Lake Road. Resources deployed include 11 engines, five air tankers, five helicopters and an air attack plane

An extra 300 firefighters have been called in to battle the fire, bringing the total headcount up to 400 firefighters. Bribiescas said winds gusted up to 35 mph.

Jenks Lake Road and the San Gorgonio Wilderness are closed. No structures have been damaged so far, though several are at risk.

Twenty to 25 residences were evacuated on Rainbow Lane in the Onyx Summit area by Thursday morning, according to the San Bernardino County Sheriff's Department.

Campground evacuations include 120 people from Camp de Benneville Pines, one person from Camp Ta Ta Pochon, 24 people from Camp Alpine Meadows, 23 people from Camp Edwards, and 10 people from Camp Tulakes. Children from the camps were bused to Citrus Valley High School in Redlands to be reunited with their parents.

Evauations also were ordered along Highway 38, east of Angelus Oaks to Onyx Summit. The road was closed Thursday morning between Angelus Oaks and Lake Williams.

Strong wind gusts are expected Thursday in the mountain community east of Los Angeles.

"This will definitely impact the firefight up in Big Bear," NBC4 forecaster Crystal Egger said.

Authorities say travelers heading up to Big Bear should use state highway 330 to highway 18, and to stay off highway 38 as that is the main route being used by firefighters.

Wildfire activity in California is nearly double the average for this time of year after a dry and warm winter, according to CalFire. The state fire agency responded to more than 1,100 wildfires that charred more than 4,200 acres between the start of the year and May.

Conditions are much drier than normal across the state, raising the risk of rapidly spreading fires.