LOS ANGELES - Local officials warned of powerful winds on Thursday that will feed wildfires raging in Los Angeles, threatening multimillion dollar mansions with blazes that have already forced more than 200,000 people to flee.

Authorities issued a "purple" alert - never used before - because of the extreme danger, warning that winds could reach 128 km/h, severely limiting firefighting efforts.

The flames have swallowed about 32,000 hectares in just over a day since the fire, currently the state's largest, broke out, leaving at least one person dead in an area about 45 minutes' drive from downtown Los Angeles.

High winds caused another wave of wildfires to erupt on Tuesday night, including one in Los Angeles' affluent Bel-Air neighborhood.

The Los Angeles City Emergency Management Department sent a wildfire emergency text message to mobile phone users in the region on Wednesday night, asking them to stay alert so that they could evacuate if necessary.

"Strong winds overnight creating extreme fire danger. Stay alert. Listen to authorities," the text message said.

"It's critically important for people that live in wildland areas that you sleep with one eye open tonight," Los Angeles county fire chief Daryl Osby said at a news conference on Wednesday.

Kate Roypirom, a resident of Porter Ranch, a community 17 kilometers west of Sylmar which has been suffering from a rapidly-spreading wildfire since Tuesday morning, said she snapped into emergency action on receiving the alert.

"I packed the important things ... (and) was ready to evacuate. My friend let us ... stay in their house," she said.

Los Angeles Mayor Eric Garcetti said more than 230,000 people had been forced from their homes in Los Angeles and Ventura counties.

In Bel-Air, that's exactly what they did.

The fire ignited on Wednesday morning and quickly grew to engulf about 150 acres around the district, home to celebrities and billionaires including SpaceX CEO Elon Musk and pop superstar Beyonce.

Police knocked on doors and used loudspeakers to make sure everybody had left their mansions.

US media reported that the Bel-Air Moraga Estate of media tycoon Rupert Murdoch, which contains a vineyard, was threatened by the wildfire.

Another wildfire, called the Skirball Fire, much closer to Los Angeles downtown, was also 5 percent contained as of Wednesday night.

The Skirball Fire blazed near the Skirball Cultural Center and the Getty Center, 25 km west of downtown and only 4 km west of the University of California Los Angeles.

The UCLA canceled all classes on Tuesday afternoon in response to heavy traffic there diverted from Skirball and also decided to put off a basketball match with the University of Montana scheduled for Wednesday night.

However, the campus is not yet included in the evacuation zone. "No evacuations are anticipated," the UCLA said in a message to students.

Xinhua - Ap