By Gillian Flaccus
The Associated Press

POPPET FLAT, Calif. — Fire crews struggled to protect homes Friday from a wind-whipped wildfire that trapped and killed four firefighters in a wall of flames as it raced across almost 38 square miles in Southern California.

The blaze, which authorities said was arson, was burning in the San Jacinto Mountains just west of Palm Springs. It destroyed 10 structures, including at least five homes. At one point, several hundred mountain residents took refuge with campers in a nearby RV park where crews could protect them.

The fire was only 5 percent contained early Friday as more than 1,100 firefighters worked to protect homes and build fire lines. Crews were sent to an area near the fire's western border late Thursday.

"We had a lot of fire activity overnight," Bill Peters, spokesman for the California Department of Forestry told The Associated Press. "Normally the fire dies down and the winds let up but that didn't happen last night. It burned like it was daytime."

Peters said firefighters had to evacuate additional areas overnight, including a small community south of Banning.

Fire officials were mourning the deaths of four U.S. Forest Service firefighters killed while attempting to protect a home close to where the fire began in Cabazon on Thursday. The flames came so quickly the five-person crew had no time to retreat to its engine or use portable fire shelters.

Authorities said a $100,000 reward would be offered for information leading to the arsonist's arrest.

"A deliberately set arson fire that leads to the death of anyone constitutes murder," Riverside County fire Chief John Hawkins said.

Authorities haven't revealed why they think the fire was arson. "Because of the seriousness, they're going to want to make sure that if and when this goes to court, they want to make sure it goes all the way," Peters said.

Three of the firefighters died at the scene and two were taken to the hospital in critical condition. One died several hours later and the other had burns over 95 percent of his body, said Pat Boss, a U.S. Forest Service spokesman.

The surviving firefighter also had severe respiratory damage, according to Dr. Dev Gnanadev, a trauma surgeon at Arrowhead Regional Medical Center.

"Overall, the chances of survival are low when you have that bad of an injury," Gnanadev said.

Boss identified his friend, Capt. Mark Loutzenhiser, a 43-year-old father of five from Idyllwild, as one of the victims. The names of the others were not released. All were based in Alandale, a small community near Idyllwild.

It was the deadliest wildfire in the United States since July 10, 2001, when four firefighters were killed in Washington's Okanogan National Forest. They became trapped by flames on a dusty dead-end road.

Thursday's deaths brought to 19 the number of California firefighters killed in the line of duty over the past year, according to statistics kept by California Professional Firefighters, a lobbying organization.

At least one civilian suffered minor injuries and 200 people in the small, mountain communities of Poppet Flat and Twin Pines were forced to flee their homes, authorities said.

In all, nearly 700 people in the area were evacuated, Gov. Arnold Schwarzenegger told reporters in Sacramento.

Timo Hargu, 61, said he rushed from his hilltop home with his two dogs after he looked out a window and saw the fire burning in a nearby valley.

"The whole thing was ablaze with flame," he said. "It was the most spectacular view. A terrible view, but spectacular."

People in the Silent Valley Club RV Resort near Poppet Flat were unable to leave after firefighters closed the only road out of the community. TV footage showed vehicles racing through smoke and flames just before the road was closed.

Firefighters said it was safer to keep the people in the RV park because the blaze was stymied by a firebreak created years earlier around the area, said sheriff's Cpl. Todd Garvin.

"This is a safe haven here. That was cleared about six years ago and it still works. It's amazing," Garvin said.

Some evacuated residents stayed temporarily in the RV park, but later were able to leave. People staying in RVs were told to remain in the park to avoid congesting the road out.

"They're fine," Peters said. "It's still too dangerous. The roads just aren't wide enough. It's easier for us to keep them there when we're on the roads with our equipment."

About 400 RVs, with 800 to 1,000 people, had registered to spend the weekend for annual Halloween events, said Silent Valley ranger Charles Van Brunt. Officials said the visitors had enough food and water because they had prepared to be there for the weekend.

Forecasters were calling for strong Santa Ana winds that could reach up to 60 mph. A "red flag warning" was in effect through Saturday night because of a mix of strong winds, low humidity and warm temperatures.

Pillars of smoke that could initially be seen in the area were quickly blown away by the strong winds and at one point the scent of smoke could be detected as far away as San Diego, 80 miles south.

As that fire raged, another sprung up in neighboring Orange County, about 50 miles southwest. There, firefighters were battling a brush fire that started overnight and forced the evacuation of about 140 people from a campground in the Cleveland National Forest near the city of Lake Elsinore, said Orange County Fire Capt. Steve Miller.

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Associated Press Writers Solvej Schou, Robert Jablon, Peter Prengaman, Jacob Adelman, Andrew Glazer and Aaron Davis contributed to this report.