FRESNO — A giant wildfire raging out of control spread into Yosemite National Park on Friday as authorities urged more evacuations in nearby communities where thousands have already been forced out by flames marching through the timbered slopes of the western Sierra Nevada.
The fire hit the park at the height of summer season, as officials geared up for a busy Labor Day weekend. It has closed some backcountry hiking but was not threatening the Yosemite Valley region, one of California's most popular tourist destinations.
The spectacular valley carved by glaciers offers visitors such iconic sights as the Half Dome and El Capitan rock formations and Bridalveil and Yosemite falls.
The weeklong blaze has spread to more than 165 square miles and was only 2 percent contained. It continued to grow in several directions, although "most of the fire activity is pushing to the east right into Yosemite," said Daniel Berlant, spokesman for the California Department of Forestry and Fire Protection.
Smoke blowing across the Sierra into the state of Nevada forced officials in several counties to cancel outdoor school activities and issue health advisories, especially for people with respiratory problems.
Authorities urged more evacuations in nearby communities where thousands have already been forced out by flames.
The fire was threatening about 4,500 residences, according to the U.S. Forest Service. Already, the blaze has destroyed four homes and 12 outbuildings in several different areas. More than 2,000 firefighters were on the lines and one sustained a heat-related injury.
While the park remained open, the blaze closed a 4-mile stretch of State Route 120, one of three entrances into Yosemite on the west side. Two other western routes and an eastern route were open.
Within the park, the blaze was burning on about 17 square miles in a remote area around Lake Eleanor, about 4 miles northwest of Hetch Hetchy reservoir, Yosemite spokeswoman Kari Cobb said.
Backcountry permits are required to hike in that area, Cobb said. The park was no longer issuing those and had contacted every person who had received a permit to go there. Two roads into that area were closed and occupants of a campground near the Route 120 west entrance were relocated.
"We don't have anybody we know of in that area based on the permits we have out now," she said.
The fire was more than 20 miles from Yosemite Valley and skies there were "crystal clear," Cobb said.
"Right now there are no closures, and no visitor services are being affected in the park," he said. "We just have to take one day at a time depending on fire activity."
The Hetch Hetchy reservoir supplies San Francisco with 85 percent of its water, but the city's Public Utilities Commission said in a statement that water quality has not been affected by the fire and was unlikely to be.
Two of three hydroelectric powerhouses in the area have been shut down because of the fire, the commission said, but the city has been able to make up the difference through buying power on the open market.