The Saddleridge fire is one of several fires burning in Southern California.

A pair of wildfires have destroyed dozens of homes near Los Angeles and forced the evacuation of hundreds of residents, fire officials said on Friday, days after authorities ordered power cuts across the state to prevent more blazes.

Fire-fighting planes and helicopters were called in to tackle two fires east of Los Angeles which spread to a combined 900 acres (360 hectares), and were described by officials as "zero per cent contained".

Authorities said an estimated 12,700 homes are facing mandatory evacuation in Porter Ranch from Reseda to De Soto, Oakridge Estates and west of Balboa, north Sesnon to the Ventura County border. The cause of the fire is under investigation.

The blaze is unpredictable, LAPD Chief Michel Moore warned, and he urged those in evacuation areas to follow orders to leave. "If you stay in [mandatory evacuation] areas we can not guarantee that we will save you". The Olivas fire quickly spread to 200 acres and was only 50 percent contained by Friday evening. The metro line in the area was also shut down. The area remains without power after the utility cut service hoping to prevent wildfires during dry, windy conditions.

Firefighters check on homes in smoke from the Saddleridge Fire in Sylmar, Calif.

There were no immediate reports of injuries. Residents were told to evacuate as a precaution, said the Brisbane Police Department.

The NWS forecasts wind gusts from 45 to 65 miles per hour across some parts of the area, saying the wind, coupled with low humidity and dry terrain, "will create critical fire weather conditions" for much of Thursday.

Although numerous blazes were quickly contained by firefighters, the risk to life and property has prompted Pacific Gas and Electric Co cut power to about 600,000 customers, a move that California Governor Gavin Newsom blamed on years of mismanagement by the utility. There are still approximately 600,000 customers in the dark.

The power was shut off earlier this week to customers in the Sierra Nevada foothills, Central Valley and San Francisco Bay Area.

"This is not, from my perspective, a climate change story as much as a story about greed and mismanagement over the course of decades".

"Turning off our customers' power is not something we take lightly, but PSPS events are one of the ways we can better ensure the safety of the public, our customers, and our employees", the company said.

The agency adds, "Wind gusts between 45 and 55 miles per hour are expected across coastal and valley areas, with gusts between 55 and 75 miles per hour in the foothills and mountains".

PG&E agreed last month to pay an $11 billion settlement over its role in contributing to wildland fires in California in 2017 and 2018 - including the Camp Fire in Butte County, the largest in California history, which killed more than 80 people last fall.