SAN FRANCISCO — Hundreds of Northern California residents have been ordered to evacuate from their homes in an Oakland neighborhood as a fast-moving fire grew along a hillside Friday afternoon, a fire official said.

Friday’s fire comes as forecasters have issued red flag warnings for fire danger until Saturday across a large swath of the state. It was not immediately clear what caused the Oakland blaze.

Oakland Fire Department spokesperson Michael Hunt said he did not have an exact figure of the evacuees but estimated that hundreds of residents had been told to leave the area.

The blaze grew to 10 acres (4 hectares) on Friday afternoon and more than 80 firefighters were working to control the flames.

No Injuries Immediately Reported

No injuries were immediately reported. Crews were called to the area around 1:30 p.m. for a vegetation fire. In less than 30 minutes, the blaze had grown, requiring more firefighters to race to the scene. By 2:30 p.m., more than 80 firefighters were working to control the blaze alongside state crews, the Oakland Fire Department said.

It was unclear if the structures that burned were homes and how badly they were damaged. The fire was near the 580 Freeway, which connects the Bay Area to central California, causing traffic jams as people tried to leave the area and smoke wafted over the city of 440,000.

Several aircraft with the California Department of Forestry and Fire Protection were dropping fire retardant and state highway officials say they shut down lanes on westbound 580 due to the fire.

Two of four 580 westbound lanes have since reopened but officials are asking people to avoid the area, said California Highway Patrol Sgt. Andrew Barclay.

Smoke was visible 2 to 3 miles (3 to 5 kilometers) away. Firetrucks and ambulances struggled to get through the gridlock in the freeway’s westbound lanes, their sirens blasting to get vehicles to move out of their way as they raced toward the blaze. The traffic frustrated some drivers enough that they exited the roadway through on-ramps, while others drove on the freeway’s shoulder. The side streets remained heavily gridlocked as well.

The fire is burning in the Oakland hills where a 1991 fire destroyed nearly 3,000 homes and killed 25 people.

The fire comes as forecasters issued red flag warnings for fire danger until Saturday from the central coast through the San Francisco Bay Area and into northern Shasta County, not far from the Oregon border.

California Utility Shuts Off Power

A California utility shut off power in 19 counties in the northern and central part of the state as a major “diablo wind” — notorious in autumn for its hot, dry gusts — spiked the risk of power lines sparking a wildfire.

About 16,000 customers were without electricity Friday after Pacific Gas and Electric shut off power.

Firefighters expect to evacuate a bigger section of the Oakland Hills neighborhood as the blaze spread Friday afternoon in the area, Oakland Fire Department spokesperson Michael Hunt told The Associated Press.

The fire began as a vegetation fire near the freeway and grew uphill, Hunt said. At least eight structures have already been damaged.

Hunt said “hundreds of residents” are being evacuated, but did not have an exact number.

“It’s a large, probably 3-mile area that’s probably potentially evacuated,” he said.

A nearby elementary school was getting set up to serve as a temporary shelter for the evacuees.

During a diablo wind, common in the fall, the air is so dry that relative humidity levels plunge, drying out vegetation and making it ready to burn. The name — “diablo” is Spanish for “devil” — is informally applied to a hot wind that blows near the San Francisco region from the interior toward the coast as high pressure builds over the West.

The “diablo wind” is forecast to cause sustained winds reaching 35 mph (56 kph) in many areas, with possible gusts topping 65 mph (104 kph) along mountaintops, according to the National Weather Service. The strong winds are expected to last through part of the weekend.

A total of about 20,000 customers could lose power temporarily in the next couple of days, PG&E said in a statement Friday.

“The duration and extent of power outages will depend on the weather in each area, and not all customers will be affected for the entire period,” the utility said.

Cause Not Known

It was not immediately clear what caused the Oakland blaze. The fire department ordered people to evacuate Friday on two streets, Campus Drive and Crystal Ridge Court. No injuries have been reported.

“This could end up being the most significant wind event for this year so far,” said meteorologist Brayden Murdock with the service’s Bay Area office. “We want to tell people to be cautious.”

Targeted power shutoffs were also possible in Southern California, where another notorious weather phenomenon, the Santa Ana winds, are expected Friday and Saturday.

Santa Anas are dry, warm and gusty northeast winds that blow from the interior of Southern California toward the coast and offshore, moving in the opposite direction of the normal onshore flow that carries moist air from the Pacific into the region.

The National Weather Service issued red flag warnings for the valleys and mountains of Los Angeles County, portions of the Inland Empire, and the San Bernardino Mountains.

Winds around greater Los Angeles won’t be as powerful as up north, with gusts between 25 and 40 mph (40 and 64 kph) possible in mountains and foothills, said Mike Wofford, a meteorologist with the weather service’s Los Angeles-area office.

The strongest winds were being recorded in the Santa Monica and San Gabriel mountains, where Friday there were gusts between 45 and 55 mph (72 and 88 kph) with isolated gusts up to 60 mph (96 kph), he said.

“Humidities are drying out and we have the winds, if we had a fire spark it could really spread quickly because of the current conditions,” Wofford said.

Meanwhile, some mountaintops around Lake Tahoe received light snowfall overnight Friday, according to the National Weather Service in Reno, Nevada. Near sub-freezing temperatures are expected again Friday night into Saturday

Wind sensors in two peaks west of Lake Tahoe registered 75 and 104 mph (120 kph and 167 kph) winds Friday with strong winds expected to continue through the night before tapering off Saturday morning, the National Weather Service said.

The service also issued its first freeze warning of the season along the Sierra’s eastern front effective from 2 a.m. to 9 a.m. Friday from south of Carson City to the north through Reno into Lassen, Sierra and Plumas counties in California where temperatures could dip into the low 20s Fahrenheit (-5 Celsius).

“Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing,” the service said.