CASTAIC, United States (AFP) — A new wildfire erupted north of Los Angeles on Wednesday, exploding in size and forcing tens of thousands of people to evacuate their homes, in a region already on edge after two deadly blazes.

Ferocious flames were devouring hillsides near Castaic Lake, spreading rapidly to cover more than 3,200 hectares in just a few hours.

The fire was being fanned by strong, dry Santa Ana winds that were racing through the area, pushing a vast pall of smoke and dangerous embers ahead of the flames — sparking fears that it could spread further.

Evacuations were ordered for 31,000 people around the lake, which sits around 56 kilometers north of Los Angeles, and close to the city of Santa Clarita.

"I'm just praying that our house doesn't burn down," one man told broadcaster KTLA as he packed his car.

The fire came with the greater Los Angeles area still suffering after two enormous fires that killed more than two dozen people and destroyed thousands of structures.

Robert Jensen, of the Los Angeles County Sheriff's Department, urged everyone in the impacted area of the new blaze — dubbed the Hughes Fire — to leave immediately.

"We've seen the devastation caused by people failing to follow those orders in the Palisades and Eaton fires," he 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."

Television footage showed police driving around neighborhoods urging people to leave.

Los Angeles County Sheriff Robert Luna said the Pitchess Detention Center in Castaic was under an evacuation order, and around 500 inmates were being moved to a neighboring facility.

He told broadcaster KCAL9 that around 4,600 inmates being held at other jails in the area were sheltering in place, but buses were on hand in case conditions changed and they needed to be moved.

California Highway Patrol said the fire was impacting traffic on the I5 freeway, with a section of the road — which runs the length of the US West Coast — shuttered.

Helicopters and planes were on the scene dropping water and retardant on the blaze.

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