The latest estimate from the Ventura County Fire Department said the blaze was only 20% contained as of 4:15 p.m.
Officials said flames have crept within 100 feet of homes in Hidden Valley as the fire veered dangerously close to luxury homes and ranches in the area. More than 1,000 firefighters were battling the blaze, with helicopters and fixed-wing aircraft flying through thick smoke to drop water and flame retardant.
Residents in Hidden Valley, the southern part of Newbury Park, and off Portrero Road have been ordered to evacuate. Evacuations in Sycamore Canyon, Deer Canyon, Brome Ranch, La Jolla Canyon, and Yerba Buena remained in effect, Ventura County fire officials said.
Evacuations for the Cal State Channel Islands campus and Dos Vientos area have been lifted but reopened to residents only.
Nick Schuler, a battalion chief with the California Department of Forestry and Fire Protection's San Diego division, said the homes most susceptible are those that haven't regularly cleared brush hundreds of feet away from their home as county firefighters suggest.
"We're in the middle of a lot of structure defense," Schuler said.
The latest tally from Cal Fire said 4,000 homes and 300 commercial properties have been threatened, with 15 residences, 15 outbuildings and five commercial properties damaged.
Area residents scrambled to flee the flames, packing cars and loading horses into trailers as authorities issued more mandatory evacuations Friday afternoon.
Sue Martin and Coleman Trainor thought the danger had passed Shelburne Farms on Portrero Road, but then they noticed the winds change. When the neighboring ranch began evacuating animals about 2 p.m., they decided they should start to make plans for the 20 horses stabled on their own property.
They worried how they would transport so many animals -- but then the trailers starting rolling in. Complete strangers showed up at the ranch, offering their help.
"This is our third load," said Lisa Riley, who helped take the horses to a Moorpark equestrian center. "We do this for them because they need the help, and I'm sure they'd do it for us."
Trainor, who is from Virginia, had never seen a wildfire before. "It's been really exciting to see the collaboration and assistance from people we don't even know," he said. "All of that has helped contribute to a successful evacuation. And now we've gotta go."
At Spirit Equestrian in Moorpark, one of the owners, Marie Knowles, said the facility was more than happy to open its stalls to ranches in need. They had taken about 35 horses in by 4 p.m. Friday, and had room for about 30 more, she said.
"Everyone who owns a horse or runs a facility plans for this kind of emergency," she said, noting her own facility had to evacuate about two years ago.
"When this kind of thing happens, people with trailers just call up facilities and say, 'Do you need help? Can you take some horses?' We all just pull together."