Originally published August 10, 2012 at 6:35 a.m., updated August 10, 2012 at 6:25 p.m.
Ground and air crews labored amid oppressive humidity and triple-digit heat today to subdue a wildfire that has blackened more than 1,650 acres and prompted evacuations in back-country territory northeast of Palomar Mountain.
Lightning sparked the blaze about 1 p.m. Thursday off Chihuahua Valley Road, east of State Route 79, authorities reported.
As of 6:30 p.m., the fire covered 1,650 acres and had been 30 percent contained, according to Cal Fire. One firefighter was hospitalized with heat-related injuries.
Personnel from local, state and federal agencies worked through the afternoon and overnight to get lines around the fast-moving flames.
As of late this morning, the burn area remained only 5 percent contained, Cal Fire Battalion Chief Nick Schuler said. No structural damage had been reported.
Firefighters were battling the blaze, dubbed the Chihuahua Fire, amid muggy conditions and temperatures reaching 103 degrees, according to Schuler.
About 7:30 p.m. Thursday, authorities began advising residents in the immediate area to pack up and leave their homes as a precaution. Overnight, so-called "mandatory'' evacuation orders -- which technically cannot be enforced in California -- went out to about 200 households.
The American Red Cross opened up a shelter for evacuees at Warner Springs High School.
Deputies also planned to clear everyone out of Lost Valley Boy Scout Camp on Chihuahua Valley Road this afternoon as a safety measure, sheriff's Lt. Paul Robbins said.