(Adds details on power restoration)
By Rollo Ross
LOS ANGELES, Oct 31 (Reuters) - A fresh spate of Southern California wildfires roared to life on Thursday, destroying homes and forcing evacuations, as the region faced a second day of explosively fierce Santa Ana winds that have fanned flames, displacing thousands of residents.
The most destructive among several new wind-driven blazes in the region erupted hours before dawn on the rugged slopes of the San Bernardino National Forest above the city of San Bernardino, barreling downhill into the north end of town.
The so-called Hillside fire quickly devoured more than 200 acres (80 hectares) of dry scrub and destroyed or damaged at least six homes before firefighters managed to keep the flames from advancing farther, fire officials said.
As of early afternoon, crews had managed to carve containment lines around 50% of the fire's perimeter. No injuries were reported, but evacuation orders remained in effect for nearly 500 homes, displacing about 1,300 residents.
The cause of the blaze is still under investigation. The San Bernardino County Fire Department said on Twitter that no power lines were located where it had originated.
The latest recurrence of Santa Ana winds, howling into the region through mountain passes from the desert, coincided with extremely low relative humidity and a prolonged lack of rainfall that has left vegetation tinder-dry across the region.
Those conditions prompted the National Weather Service to create a new alert level, issuing an "extreme red-flag warning" for fire danger in Los Angeles and Ventura counties.
Winds were beginning to subside on Thursday, though red-flag warnings were extended through Friday evening in mountain and foothill areas deemed especially susceptible to high gusts.
The latest Santa Anas cap a flurry of extreme windstorms across California during the past month, but once they dissipate no more were forecast for at least the next week, Weather Service meteorologist Kristen Stewart said.
The easing winds helped firefighters make short work of numerous blazes that sprung up early Thursday, and to consolidate gains against a pair of major fires ignited earlier in the week.
A fire that erupted early on Monday near the famed Getty Center art museum in west Los Angeles, threatening thousands of homes in some of the city's wealthiest neighborhoods, was largely suppressed by Thursday, with containment listed at 40%.
Residents were allowed to return to most of the 10,000 homes that had been ordered evacuated.
The museum emerged unscathed, but about a dozen dwellings were lost in the 745-acre Getty fire and two firefighters were injured.
Investigators say the Getty fire was likely caused by a broken tree branch blown into power lines by high winds.
Hollywood production designer Marek Dobrowolski, returning to his fire-scarred neighborhood after three days, found his home intact but said the ordeal was nonetheless "traumatizing."
He added that utilities should be burying more of their power lines underground to prevent such calamities.
"You should not have a fire that starts with a branch that falls into wires, and then 12 houses are burned down and 17,000 people have to evacuate," said Dobrowolski.
About 30 miles (48 km) to the northwest, a fire that raged to the edge of the hilltop Ronald Reagan Presidential Library in Ventura County's Simi Valley on Wednesday was 10% contained on Thursday after threatening thousands of homes.
Some 26,000 residents were ordered to flee at the height of that blaze, dubbed the Easy fire, along with an unknown number of horses and other livestock in an area dotted with ranch properties. Firefighters managed to keep flames from damaging the Reagan Library compound.
By Thursday, the Easy fire had scorched more than 1,700 acres, leaving fire crews focused on mopping up hot spots. County schools remained closed, but evacuation orders were lifted.
High winds also left thousands of people in the region without electricity, either from downed power lines or from utilities selectively shutting off power to reduce the risk of wildfires being sparked by damaged wires.
Pacific Gas and Electric Co acknowledged last week that the Kincade fire, a blaze that charred 77,000 acres of Sonoma County wine country north of San Francisco, started last week near a damaged PG&E transmission tower at about the time a high-voltage line on that tower malfunctioned.
That blaze has destroyed at least 266 homes and other structures, but was listed as 60% contained on Thursday.
PG&E, which over this past weekend began shutting off power to 940,000 customers in the state to guard against the risk that an electric mishap could spark a blaze, said in a statement on Thursday it had restored electricity to all but 6,700 customers.
Wind damage to power lines was not the only fire-causing danger. A 300-acre blaze in Riverside County, east of Los Angeles, ignited when a high-speed police pursuit of a stolen vehicle ended in the crash of the suspect's car early on Thursday, authorities said. (Reporting by Rollo Ross in Los Angeles; Additional reporting and writing by Steve Gorman in Culver City and Jonathan Allen in New York; Additional reporting by Alex Dobuzinskis in Culver City Editing by Scott Malone, Bill Berkrot and Rosalba O'Brien)