A "difficult" wildfire that prompted mandatory evacuations in the Refugio Canyon area of Santa Barbara County grew to an estimated 1,400 acres Thursday, and was being fanned overnight by winds gusting up to 45 mph.
Chaparral, tall grass and dry brush in the Los Padres National Forest were providing fuel for the flames.
The fuel in that area has not burned since 1955, and crews were struggling to hold a fire line, a news release from Santa Barbara County said.
Authorities are referring to the blaze as both the Scherpa Fire and the Sherpa Fire. The fire was 0 percent contained as of early evening.
The fuel, the topography and the weather were providing challenging conditions for firefighters. It was in the 70s in the area of the fire Thursday, with gusty winds, according to the National Weather Service forecast.
Evening sundowners -- fierce winds that are particularly dangerous during wildfires and come down from the mountains toward the coast -- are expected to further test the response.
Just before 9 p.m., authorities were forced to shut down the 101 Freeway between Winchester Canyon and Mariposa Reina. The freeway was expected to remain closed throughout the night.
The highway was closed overnight Wednesday from Buellton to Goleta, reopening around 7:30 a.m. Thursday.
Firefighters are concerned about 60 homes in Refugio Canyon and 80 homes in El Capitan Ranch, as well as the Circle Bar B Ranch and an area called "The Narrows."
"This is a significant and difficult incident,” Santa Barbara County Fire Department Chief Eric Peterson said. “Conditions and terrain are dangerous, making it difficult for crews to reach."
The fire, which had burned about 250 acres Wednesday, grew to an estimated 1,200 acres by about 8:30 a.m. Thursday, according to the InciWeb page. Aircraft were not able to get a more exact acreage estimate due to low-lying smoke.
About 1 p.m. Thursday, the blaze was burning a quarter-mile from the 101 Freeway near the Refugio Campground.
During a Thursday morning news conference, Peterson said the blaze was expected to grow.
“Obviously, it’s going to get bigger," Peterson said. "It’s getting bigger as we speak."
U.S. Forest Service firefighters were responding alongside county firefighters, and Cal Fire was also at the scene.
Mandatory evacuations were in place for areas of Refugio Canyon, Las Flores, Venadito, El Capitan Campground, El Capitan Canyon, El Capitan Ranch and Refugio Campground. About 400 residents are under mandatory evacuation, officials said.
An evacuation center was set up at the Wake Center, located at 300 North Turnpike Road in Goleta, and Santa Ynez Union High School, according to the InciWeb page. Large animals can be taken to the Earl Warren Show Grounds.
More than 800 personnel were responding to the blaze, as were 61 fire engines and 30 aircraft, according to a Santa Barbara County new release issued early Thursday evening.
A heat wave was expected to hit the region over the weekend.
An air-quality warning is in effect for the southern areas of Santa Barbara County through the weekend, unless conditions change, officials said.
The cause of the fire is under investigation.