LANCASTER, Calif. – An army of firefighters toiled Thursday morning to prevent a massive fire from consuming communities in the Lake Hughes area after the blaze exploded to more than 10,000 acres in just a few hours.

Officials warned that containing the Lake fire – which started in the Angeles National Forest near Interstate 5 Wednesday and rapidly roared through stands of pine trees – will be a lengthy and arduous process. The battle is made more difficult by rugged terrain and thick vegetation that, in some areas, hasn’t burned in several decades.

“This will be a major fire for several days,” Angeles National Forest Fire Chief Robert Garcia said during a news conference Thursday.

After igniting shortly after 3:30 p.m. Wednesday, the fire moved toward several small communities on the Antelope Valley floor west of Lancaster. It burned rapidly to the northeast Wednesday evening, toward Highway 138.

By sunrise Thursday, the blaze had chewed through 10,500 acres and destroyed three structures. More than 5,000 buildings remain threatened, according to officials with the Los Angeles County Fire Department.

L.A. County Fire Chief Daryl Osby said crews had actively battled the blaze throughout the night.

“We can say that many structures were saved because of the actions of the firefighters last night,” he said. “They were up all night.”

The weather late Wednesday and early Thursday brought a welcome reprieve, with cloud cover and even an occasional drizzle in the burn area, but temperatures are expected to soar heading into the afternoon.

“The current weather that we started with this morning has helped buy us some time,” Garcia said.

The National Weather Service has issued excessive heat warnings in Southern California for Friday through Monday evening.

“Today, hot air temperatures in the 90s to 100s, lower relative humidities and drying fuels will bring elevated fire weather conditions,” officials wrote in an incident update for the Lake fire Thursday morning. They added that “extreme and aggressive fire behavior” was expected, exacerbated by the area’s steep topography, with spot fires and rapid growth of the blaze.

That combination of thick vegetation and hot, dry and windy conditions is fueling the fire, according to Seneca Smith, a public information officer with the Angeles National Forest.

“Current objectives include keeping the fire north of Castaic Lake, south of Highway 138, east of Red Rock Mountain and west of Tule Ridge,” officials wrote in the incident update.

More than 1,000 personnel, as well as several helicopters and fixed-wing aircraft, have been deployed to the scene, with assistance provided by the L.A. County Fire Department, the Angeles National Forest and numerous fire departments in the area.

The cause of the fire is under investigation, but Osby said that “over 90 percent of fires are human caused” every year, underscoring the need to be cautious and prepared.

“It’s going to be a hot, dry summer,” he said, “and it’s going to be a very, very hot, dry weekend.”