SAN FRANCISCO (AP) — A fast-spreading wildfire damaged at least eight buildings in the Oakland hills in Northern California on Friday, triggering an evacuation order as the area grew to 10 acres (4 hectares).

No injuries were initially reported. Emergency crews were called to the area around 1:30 p.m. due to a vegetation fire. The fire spread in less than 30 minutes, forcing additional firefighters to rush to the scene. As of 2:30 p.m., more than 80 firefighters along with state responders were working to bring the fire under control, the Oakland Fire Department said.

It was unclear whether the burned buildings were residential buildings and how badly damaged they were. The fire occurred near the 580 Freeway, which connects the Bay Area with central California, causing traffic jams as people tried to leave the area and smoke billowing over the city of 440,000.

Multiple California Department of Forestry and Fire Protection aircraft dropped fire retardant and state highway officials said they closed westbound lanes on the 580 due to the fire.

Smoke was visible 2 to 3 miles (3 to 5 kilometers) away. Fire trucks and ambulances struggled to get through traffic jams in the highway’s westbound lanes, their sirens blaring to encourage vehicles to get out of their way as they raced toward the fire. The traffic frustrated some drivers so much that they drove off the road on ramps while others drove on the shoulder of the highway. The side streets also remained heavily congested.

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

The fire comes at a time when forecasters have issued fire warnings through Saturday from the central coast across the San Francisco Bay Area to northern Shasta County, not far from the Oregon border.

A California utility has shut off power in 19 counties in the north-central part of the state as a strong “Diablo wind” – notorious for its hot, dry gusts in the fall – increased the risk that power lines could spark a wildfire .

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

Firefighters expect to evacuate more of the Oakland Hills neighborhood as the fire spread through the area Friday afternoon, Oakland Fire Department spokesman Michael Hunt told The Associated Press.

The fire started as a vegetation fire near the highway and spread uphill, Hunt said. At least eight structures have already been damaged.

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

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

A nearby elementary school was being set up as temporary housing for the evacuees.

During a Diablo wind, which is common in the fall, the air is so dry that relative humidity drops, vegetation dries out and is ready to burn. The name – “Diablo” is Spanish for “devil” – is used informally for a hot wind that blows inland toward the coast near the San Francisco region as high pressure builds to the west.

According to the National Weather Service, the “Diablo wind” is expected to produce sustained winds of 35 mph (56 km/h) in many areas, with possible gusts of up to 65 mph (104 km/h) on mountain peaks. Strong winds are expected to continue for part of the weekend.

In total, about 20,000 customers could temporarily lose power over the next few days, PG&E said in a statement Friday.

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

It was not immediately clear what caused the Oakland fire. Fire officials on Friday ordered people to evacuate on two streets, Campus Drive and Crystal Ridge Court. No injuries were reported.

“This could be the most significant wind event so far this year,” said meteorologist Brayden Murdock of the service’s Bay Area office. “We want to tell people to be careful.”

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

Santa Anas are dry, warm, gusty northeasterly winds that blow toward and offshore from the interior of Southern California, moving in the opposite direction of the normal overland 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, parts of the Inland Empire and the San Bernardino Mountains.

Winds in the Los Angeles area will not be as strong as in the north, with gusts between 25 and 40 miles per hour (40 and 64 km/h) possible in mountains and foothills, said Mike Wofford, a meteorologist at the weather service’s Los office Angeles.

The strongest winds were recorded in the Santa Monica and San Gabriel mountains, where there were gusts between 45 and 55 miles per hour (72 and 88 km/h) with isolated gusts up to 60 miles per hour (96 km/h) on Friday he said.

“The humidity is drying out and we have winds. If we had a spark of fire, it could spread very quickly given the current conditions,” Wofford said.

According to the National Weather Service in Reno, Nevada, some mountain peaks around Lake Tahoe received light snow overnight Friday. Temperatures near freezing point are expected again from Friday evening to Saturday

Wind sensors on two peaks west of Lake Tahoe recorded wind speeds of 75 and 104 miles per hour (120 km/h and 167 km/h) on Friday. Strong winds are expected to continue through the night before easing Saturday morning, the National Weather Service said.

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

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

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Dazio reported from Los Angeles.