Wildfire near LA spreads to more than 15,600 acres, 20% containment

A wind-whipped Southern California wildfire that started over the weekend ballooned to more than 15,600 acres on Monday, prompting the evacuation of more than 1,000 campers from a park, closing a popular recreation area on Father's Day and threatening a major freeway in and out of Los Angeles, authorities said.

The Post Fire, which began after 2 p.m. PT on Saturday near Gorman, California, in the Tejon Pass area of Los Angeles County, saw flames jump from 5,000 acres to 14,625 acres by Sunday evening, according to the California Department of Forestry and Fire Protection (Cal Fire).

By mid-morning Monday, the fire spread to 15,610 acres, fueled by dry brush and wind gusts of 50 to 65 miles per hour, according to Cal Fire and National Weather Service. Firefighters managed to increase containment from 2% on Sunday to 8% on Monday, eventually reaching 20% containment Monday night, according to Cal Fire.

More than 1,140 firefighters, including air tankers and helicopter crews, are battling the fire from the ground and sky, authorities said.

Joe Sirard, a meteorologist for the National Weather Service in Oxnard, California, told ABC News a red flag warning signaling high fire risk has been issued for the area until at least 6 p.m. Tuesday. Sirard said gusty winds of more than 60 mph are forecast for the area Monday night.

Capt. Sheila Kelliher Berkoh of the Los Angeles County Fire Department said firefighting conditions were challenging due to the high wind gusts, low humidity of around 15% and temperatures in the low to mid-80s.

"It's hot, it's windy, it's super slippery," Berkoh told ABC News Monday of the area where firefighters are battling flames. "Those ridgelines are tough and with the fire coming at you, you can't make a direct attack at that. So, you're really trying to come around the side."

She said 11 bulldozers were being used to cut containment lines as firefighters gained a handle on the fire from the ground.

Berkoh said firefighters are crossing their fingers and praying that the fire, now moving from the north to the west into remote vacant areas, doesn't shift.

"Let's hope that it doesn't change direction and push the fire to the east because that's into a little more populated area and then we'll have a big fight on our hands," Berkoh said.

Three hikers who were stranded when their off-road vehicle broke down in the fire zone had to be rescued Sunday morning, the Los Angeles County Fire Department told ABC News. The rescued hikers were taken to a hospital and treated for minor injuries, officials said.

At least one structure was destroyed by the fire, Cal Fire said. The cause of the fire remains under investigation.

About 1,200 campers at the Hungry Valley Park State Vehicular Recreation Area were ordered to evacuate Saturday night, and authorities closed Pyramid Lake, which was expecting thousands of visitors for Father's Day, due to the threat of the Post Fire, Cal Fire said.

The fire was burning parallel to Interstate 5, a major arterial highway in and out of Los Angeles. The freeway was briefly closed on Saturday, triggering a traffic jam, officials said.

Meanwhile, a second Southern California wildfire was burning near Hesperia in San Bernardino County. The blaze started about 6:49 p.m. PT on Saturday and had burned 1,078 acres by Sunday afternoon, according to Cal Fire.

The wind-driven fire was pushing east Sunday toward the Arrowhead Equestrian Estates in Hesperia, where residents remained under an evacuation warning Monday, according to Cal Fire.

The Hesperia Fire is 72% contained as of Monday evening. There are no immediate reports of injuries or damage and the cause remains under investigation.