The North Pass fire in Mendocino County has grown to 18,500 acres, spreading in all directions but west toward the nearest population center in Covelo, Cal Fire said.
Still, evacuations have been necessary, most recently along the Mendocino Pass Road-Forest Highway 7 that runs east out of Round Valley toward the Tehama-Glenn county line, officials said.
An estimated 30 additional homes -- many of them used only as weekend or vacation homes -- were included in the evacuation area announced Wednesday afternoon, Mendocino County sheriff's officials said.
All told, up to 80 residences, only some of them occupied year-round, are under mandatory evacuation, authorities said. Sheriff's personnel also have cleared out campgrounds and back-country trails around the fire, which was ignited by a lightning strike in dry timber outside Covelo early Saturday morning, fire officials said.
The fire started about 10 miles east of Covelo in Round Valley, north of Mendocino Pass Road in heavy timber outside the Mendocino National Forest.
The area is remote and rugged, making it difficult to move equipment around and making firefighting hazardous, fire officials said. At least three people have suffered minor injuries, like twisted ankles, so far.
A total of 962 firefighting personnel, the majority from Cal Fire, were battling the fire Thursday.
Cal Fire said early Thursday that the blaze was 10 percent contained, a slight drop from the 11 percent containment declared a day earlier.
Spokeswoman Julie Cooley said she understood existing containment lines had held, but with the expanding circumference of the fire it amounted to a smaller percentage.
Arriving early Thursday at the fire area where he was going to assist with roadblocks at road closures, sheriff's Capt. Kurt Smallcomb said holding the western front was clearly imperative as far as public safety was concerned. "As long as it keeps on moving east, as far as any residences or further evacuations, we should be good with that," he said.