SANTA BARBARA  (AP) — A surging wildfire forced thousands of people, most of them Memorial Day campers, to evacuate the mountains of California’s Santa Barbara County, officials said.

The fire broke out about 2:45 p.m. Monday in Los Padres National Forest about 15 miles north of Santa Barbara, and hours later had grown to 1,000 acres — or 1.5 square miles — amid winds of about 20 mph, U.S. Forest Service officials said. It was 5 percent contained.

The fire was threatening about 50 homes, many of them cabins and vacation rentals, and 50 to 75 residents had evacuated, county fire Capt. David Sadecki said.

Paradise Road and the many campgrounds along it were closed, forcing thousands of campers, many already clearing out at the end of the holiday weekend, to evacuate, officials said.

A U.S. Forest Service garage and two vehicles had burned, Sadecki said.

The American Red Cross set up an evacuation center at Santa Barbara City College and another was set up for horses stalled in the area’s many stables.

The National Weather Service said the winds may get worse as night falls, but fire officials said they may also get help from the weather.

“We’re hoping the temperatures drop and the humidity rises,” Sadecki said.

A huge plume of gray and white smoke rose over the mountains and hovered over Santa Barbara, where many residents were flooding Facebook and Twitter with photos.

The county has issued an air quality warning because of the smoke and wind, advising people to limit time spent outdoors and to avoid outdoor exercise altogether.

To the south, a fire in San Diego County wilderness has scorched 900 acres of dry brush but was not a threat to homes or buildings.

The blaze southeast of Julian was sparked around midday Sunday in the Banner Grade area, and fire officials were investigating whether it was set intentionally.

It was 43 percent contained Sunday night, fire officials said.