LOS ANGELES (Reuters) - A massive wildfire roaring through mountains north of Los Angeles forced some firefighters to retreat Monday as it menaced foothill homes and Mount Wilson, a broadcasting hub and site of an historic observatory.
The so-called Station Fire more than doubled in size as it burned out of control for a sixth day, charring 105,000 acres, up from 42,000 acres late Sunday, and sending up towering plumes of smoke that fouled the air for miles (km) around.
Two firefighters died Sunday when they were overrun by flames in the Angeles National Forest and rugged San Gabriel Mountains. Nearly 2,600 firefighting personnel, some from as far away as Montana and Wyoming, were battling the blaze.
Fire crews fought to protect the slopes around the 5,700-foot (1,740-meter) peak of Mount Wilson, home to 50 buildings plus a world-famous array of telescopes and a critical cluster of transmission towers for broadcasters.
After dousing the area in fire retardant and laboring to clear brush away from structures on the site, they fell back to avoid the flames expected to engulf the area.
"They've done everything they can do and it's unsafe for them to be there when the fire hits," Los Angeles County Fire Captain Mark Whaling said.
Elsewhere in the forest, 65 firefighters retreated from a wall of flames advancing on their positions, he said.
Rescue teams were standing by to save five people who became trapped in the forest after they disregarded evacuation orders, authorities said.
Eighteen houses were destroyed Sunday and at least three structures were reported lost early Monday, said Scott Visyak, spokesman for the California Department of Forestry and Fire Protection.
The fire threat eased in some foothill communities of suburban Los Angeles that had been menaced over the weekend. But other neighborhoods were now at risk, including 200 to 300 homes on the southwest flank of the blaze just inside Los Angeles city limits.
Residents there were ordered to evacuate, city fire department Captain Steve Ruda said.
Throughout the fire zone some 4,000 dwellings have been ordered evacuated, said Stephen Whitmore, spokesman for the Los Angeles County Sheriff.
Four men and one woman who defied such orders ended up trapped in a home surrounded by flames and were calling for help. Whitmore said rescue teams would go in to get them when they could.
The first day of classes for two school districts were canceled due to heavy smoke, and the Los Angeles Department of Water and Power asked customers to curb electric use in case of potential fire damage to a pair of 500-kilovolt transmission lines northeast of the town of Acton.
The fire was just 5 percent contained and may not be fully contained for another eight days, officials predicted.
The blaze was being fueled by dense, tinder-dry vegetation that had not burned in decades, triple-digit temperatures and low humidity. But so far the Santa Ana winds that have fanned many of Southern California's worst wildfires in recent years were absent.
Three civilians were reported injured over the weekend, including two who failed to heed evacuation orders and sought shelter in a hot tub when the flames arrived.
Editing by Dan Whitcomb and Xavier Briand