LOS ANGELES (AP) — A new large wildfire broke out Wednesday in Southern California amid gusty winds, forcing the evacuation of the Ronald Reagan Presidential Library and nearby homes.

The brush fire started just before dawn in the Simi Valley area north of Los Angeles, Ventura County officials said.

They tweeted that the fire was large without providing details on its size and said it was burning between the cities of Simi Valley and Moorpark.

Officials did not immediately say how many people were subject to evacuation orders.

Meanwhile, frustration and anger mounted across Northern California as Pacific Gas & Electric Co., the state’s largest utility, began the third round of sweeping blackouts in a week aimed at preventing its electrical equipment from being fouled by wind-whipped branches or toppling and sparking wildfires.

PG&E said Tuesday’s blackouts would affect about 1.5 million people in some 30 counties including the Sierra foothills, wine country and San Francisco Bay Area. They included 1 million still without power from a shut-off over the weekend.

In wine country north of San Francisco, firefighters coped with gusts while tackling a wildfire that has burned 86 homes and charred an area more than twice the size of San Francisco. About 90,000 buildings remained threatened. More than 150,000 people were under evacuation orders.

Winds topped out at 70 mph north of San Francisco Bay and began to ease early Wednesday, but forecasters said fire danger would remain because of continuing breezes and very dry air.

In Southern California, Santa Ana winds developed more slowly Wednesday than expected but were topping 50 mph in some areas before dawn.

The National Weather Service said the strongest winds were to the west of the section of Los Angeles where a wildfire destroyed a dozen homes on Monday.

That fire was caused when a dry branch from a eucalyptus tree was flung 30 feet by high winds into a city Department of Water and Power line, which short-circuited and sparked, the utility and Fire Department announced Tuesday.

The power line had been operating safely and the DWP had cut away brush and trees from around the line, officials said.

Mayor Eric Garcetti called it an “act of God.”

The National Weather Service called an extreme red flag warning for much of Southern California through Thursday evening, with some wind gusts reaching 80 mph. It could be the strongest wind event in years.

Coupled with tinder-dry brush and low humidity, they could blow the smoldering fire back to life and spread embers to start new blazes, authorities warned.

Southern California Edison, which had previously made safety shutoffs and then restored power, cut power to 38,000 customers and warned that it could black out more than 300,000 customers, or some 600,000 people.

Also Tuesday, Edison announced in a quarterly earnings report that it was “likely” its equipment caused last year’s Woolsey Fire, which killed three people and destroyed hundreds of homes in a swatch stretching from north of Los Angeles south through Malibu to the sea.

No deaths were reported from the current fires but weekend gusts may have claimed three lives. A 55-year-old homeless woman was crushed by a falling tree during high winds Sunday at a Santa Cruz campsite and a couple was killed the same day in a remote area of Madera County when a tree fell on their Jeep, which then crashed.