(Updates with fire growing, power lines threatened, evacuation lifted)

By Steve Gorman

LOS ANGELES, July 30 (Reuters) - A fierce brush fire nearly doubled in size overnight as it threatened power lines that supply electricity to the greater Los Angeles area, but evacuation orders for 2,000 homes were lifted, officials said on Friday.

The blaze, dubbed the Crown Fire, erupted Thursday afternoon and quickly spread across 4,500 acres of tinder-dry chaparral and scrub in rolling hills near the city of Palmdale, about 35 north of Los Angeles.

By Friday morning, the blaze had grown to some 8,000 acres and was encroaching on key power lines operated by the Los Angeles Department of Water and Power and Southern California Edison, Los Angeles County fire inspector Don Kunitomi said.

He said protecting those lines, which deliver power to the metropolitan Los Angeles area, was one of the top priorities of some 750 firefighters battling the flames on the ground.

At daybreak, the fire department relaunched a major aerial assault on the blaze with water-dropping helicopters and airplanes, officials said.

The threat of widespread damage to homes appeared to have been eased early Friday as evacuation orders for some 2,000 homes in the unincorporated town of Leona Valley and nearby south Palmdale were lifted.

But Kunitomi said three trailer homes had gone up in flames since the blaze began, along with a hay barn and three outbuildings. Unconfirmed local media reports said a house also had been consumed by flames.

No injuries have been reported, Kunitomi said.

The Leona Valley area, about 35 miles north of downtown Los Angeles, is an agricultural community known for its peach, apple and cherry orchards, as well as ranches for horses, sheep and other livestock.

One rancher told KNX radio on Friday that the fire burned through part of his property, but skirted an area where he had eight bison grazing. (Writing and reporting by Steve Gorman; Editing by Jonathan Oatis)

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