SANTA BARBARA, Calif. (AP) - Shifting winds posed new challenges for firefighters battling a blaze in Southern California coastal mountains that threatened ranches and rural homes and kept a major highway shut down for days.

The Alisal Fire charred more than 24 square miles of dense chaparral in the Santa Ynez Mountains west of Santa Barbara. Containment was just 5% Wednesday evening.

While the scenic region along the Pacific shoreline is lightly populated, the blaze was a threat to more than 100 homes, ranches and other buildings, fire officials said.

Fire crews were protecting Rancho del Cielo, which was once owned by Ronald and Nancy Reagan and was known as the Western White House during his presidency. The 688-acre ranch where Reagan hosted world leaders sits atop the mountain range, above the flames feeding on dense chaparral and grasses.

Based on staff reports from the ranch, the fire was about a half-mile away Wednesday evening, but that section of the blaze was not as active as others, said Jessica Jensen, vice president and chief of staff of the Young America’s Foundation, which now operates the ranch.

“We are thankful that there has been no fire activity on the actual Reagan Ranch property. The Ranch, itself, is still in a very defensible position,” Jensen said in an email to The Associated Press.

The area hadn’t burned since 1955, according to the conservative youth organization.

Fire engines were on the ranch property, and fire retardant will be sprayed around its structures, the foundation said in a statement.

It noted that helicopters have filled up with water from one of the ranch’s two lakes.

Crews also protected an Exxon Mobil Corp. gas processing facility in a canyon surrounded by flames.

The fire erupted Monday near the Alisal Reservoir, and powerful winds from the north swept the flames down through the mountains, forcing the closure of U.S. 101 in western Santa Barbara County. At one point, the fire jumped the four-lane highway and reached a beach.

The closure has forced motorists to take a circuitous detour on smaller routes.

The highway could remain shut until the weekend, said Andrew Madsen, a spokesman for the U.S. Forest Service.