A fast-moving wildfire broke out in the mountains north of Los Angeles and ripped through an estimated 21 square kilometres (8.1 square miles) of trees and brush leading to thousands of evacuation orders for local residents and sending an enormous plume of dark smoke into the sky.

Firefighters said on Wednesday the Hughes Fire in the Castaic Lake area of Los Angeles County – located about 80km (50 miles) north of the city of Los Angeles – prompted evacuation orders to local residents amid the “immediate threat to life” due to the blaze.

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An estimated 18,600 people live in the local community where ferocious flames devoured trees and brush on the hillsides around Castaic Lake.

Robert Jensen of the Los Angeles County Sheriff’s Department urged everyone in the fire-affected area to leave immediately and not suffer the same fate as some in the devastating fires that hit the Los Angeles area of Eaton and Palisades, as well as other areas, that killed 28 people and left thousands homeless.

“We’ve seen the devastation caused by people failing to follow those orders in the Palisades and Eaton fires,” Jensen said.

“I don’t want to see that here in our community as well. If you’ve been issued an evacuation order, please get out,” he said.

US television news showed police driving around the Castaic area urging people to leave as crews on the ground and in water-dropping aircraft fought to prevent the wind-driven fire from moving southward towards more populated foothill communities.

The blaze was fanned by strong, dry Santa Ana winds that raced through the area, pushing a vast pall of smoke and embers ahead of the flames.

Firefighting crews from the Los Angeles County Fire Department and Angeles National Forest were also attacking the blaze from the ground.

It was not immediately known what sparked the fire, but it occurred during red flag fire conditions when meteorologists say strong winds and low humidity create conditions ripe for rapid fire spread.

The University of California San Diego shared dramatic video of the start of the Hughes Fire and its rapid development on its ALERTCalifornia online platform, showing a huge cloud of smoke developing quickly as the fire spreads across hillsides.

US President Donald Trump, who criticised the response to earlier wildfires in the Los Angeles area during his inaugural address on Monday, said he will travel to the city on Friday.

As the new fire raged in Castaic, the Eaton and Palisades fires – that have also ravaged Los Angeles – have been brought under greater control, the California Department of Forestry and Fire Protection (Cal Fire) said.

The Eaton Fire, which has burned through 5,674 hectares (14,021 acres) east of Los Angeles, is now 91 percent contained, while the larger Palisades Fire, which has consumed 9,489 hectares (23,448 acres) on the west side of Los Angeles, is almost 70 percent contained, authorities said.

Since the Eaton and Palisades fires broke out on January 7, they have killed 28 people and damaged or destroyed nearly 16,000 structures, Cal Fire said.

At one point, during the height of the fires, 180,000 people were under evacuation orders, according to Los Angeles County officials.

Private forecaster AccuWeather projects damage and economic losses from the fires around Los Angeles at more than $250bn.