LOS ANGELES (Reuters) - A California wildfire forced the evacuation of hundreds of homes as it raged largely unchecked through mountains north of Los Angeles, stoked by dense, desiccated chaparral and timber that last burned some 50 to 100 years ago, fire officials said on Thursday.

The blaze has scorched some 10,500 acres (4,249 hectares) since erupting Wednesday afternoon near Lake Hughes in the Angeles National Forest. As of Thursday afternoon, it remained at zero percent containment, despite a light morning rain over the area, U.S. Forest Service spokesman Andrew Mitchell said.

Temperatures in the region were expected to rise above 100 degrees Fahrenheit later in the day, he said.

More than 1,000 firefighters were assigned to the blaze, dubbed the Lake Fire, which was believed to have been sparked by human activity, though the precise cause remained under investigation, Mitchell said.

No casualties were reported as of Thursday, but the blaze has prompted the mandatory evacuation of some 500 homes in the communities of Lake Hughes and Leona Valley, about 40 miles (65 km) north of downtown Los Angeles, according to Mitchell.

Thick, extremely dry vegetation, some of which has not burned in about a century, was fueling the flames that roared swiftly up steep canyons and hillsides, he said.

"This will be a major fire for several days," U.S. Forest Service regional Fire Chief Robert Garcia told reporters.

"The current weather that we started with this morning has helped buy us some time to get some relief crews out there and start developing some preventive control anchor points," Garcia said.

Los Angeles County Fire Chief Daryl Osby said the fire had destroyed several structures, though many were saved "because of the actions of the firefighters last night, who were up all night."

The Angeles National Forest, covering some 700,000 acres, is a popular outdoor destination for millions who live in the sprawling L.A. metropolitan on its southern flanks.

Year to date, California wildfires have charred more than 227,000 acres statewide, records show.

 

(Reporting and writing by Steve Gorman in Los Angeles; Additional reporting by Peter Szekely in New York; Editing by Alistair Bell, Bill Tarrant and Tom Brown)