FRESNO, Calif. — 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 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.
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.
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 US 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.