LOS ANGELES – A wildfire fanned by erratic winds chased thousands of people from their homes in a mountaintop town 80 miles east of Los Angeles, officials said on Sunday.

The so-called Sheep Fire, which has charred 4,000 acres since Saturday afternoon, reached the outskirts of Wrightwood, a bucolic resort in the San Gabriel Mountains with a population of about 4,000.

It has destroyed at least three homes, but is threatening at least 2,000 more, said Capt. Jason Megowan, a spokesman for the San Bernardino National Forest Service. The cause of the fire was unknown.

Authorities issued a mandatory evacuation order for Wrightwood as they struggled to combat the fire through a combination of aerial assaults and backfires. Unpredictable winds, with gusts of up to 50 miles an hour, made their jobs difficult.

The fire could conceivably burn from east to west across the San Gabriels, bumping into the area that was blackened last month by the largest wildfire in the recorded history of Los Angeles County. The so-called Station Fire laid waste to more than 160,000 acres of terrain, destroyed dozens of dwellings and led to the deaths of two firefighters, whose truck fell off a mountain road.