A fire burning in Los Angeles' San Gabriel Mountains proved tough to contain as holiday campers were forced to evacuate the area over the Labor Day weekend. KNBC's Robert Kovacik reports.

A brush fire in the San Gabriel Mountains that prompted the evacuation of campers and picnickers in the hills above Glendora, Calif., continued to rage Tuesday and it could be several days before crews gain the upper hand.

"We have some challenges we face out there," Tony Imbrenda, of the Los Angeles County Fire Department, told NBCLosAngeles.com. "We expect that this is going to take several days to get some containment."

Crews continued the aerial attack on the fire burning east of Los Angeles and about 10 miles south of Highway 2. The terrain was described as "very steep."

Four people, including at least two firefighters, had been injured, suffering from heat-related ailments, Angeles National Forest Officer Angie Lavell told the Los Angeles Times, though none of the four required hospitalization.

The fire, which started Sunday and has burned 3,600 acres, was moving toward Rattlesnake Canyon Ridge. Fire officials said the goal was to stop the fire there.

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Some 1,000 people, many of them enjoying the three-day holiday, were evacuated from several communities and from three campgrounds as the fire spread in the largely recreational area.

David Mcnew / Getty Images The Williams Fire spreads as night falls in the Angeles National Forest on Monday north of Glendora, Calif.

Los Angeles County Sheriff's deputies searched hillside trails for any hikers who were still walking in the hills. The evacuations started after 3 p.m. Sunday in the area off of San Gabriel Canyon Road in Azusa. Officials closed roads leading into the hills.

Highway 39 was closed early Monday.

The fire is named after Camp Williams, which, according its the website, is a "quiet haven tucked away in the spectacular San Gabriel Mountains." It offers camping, swimming, fishing, hiking, biking, and panning for gold. The camp, located at the San Gabriel River East Fork has full-hook-up RV sites under giant oak trees.

The fire was burning uphill into heavy timber and steep, rugged terrain, fire officials said.

A gray plume of smoke could be seen by commuters for miles.

Nearly 800 firefighters, backed by 10 helicopters and four air tankers, were battling the blaze. Containment was at just 15 percent Tuesday morning.

Maritza Martinez got out of the area when she noticed smoke.

"When we came up, we noticed a whole bunch of smoke and we started to notice something is burning and little by little the smoke started to grow," she said. "My little sister was like, 'Let's go! Let's go!'"

The experience was a first for Catharine Vega, one of nearly 12,000 visitors who had expected to use the park during the holiday weekend.

"I've never seen a real fire except on TV," she said. "We stopped to see, and we saw actual flames and it was scary because we didn't know what to do."

NBCLosAngeles.com contributed to this report.

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