The Route Fire, which sparked near the 5 Freeway in Castaic, had burned through 5,200 acres by Thursday morning as a punishing heatwave settled in on the state.
The highway was shut down, and evacuations have been ordered for anyone in the immediate area of the road near Castaic Lake. Evacuation shelters have been set up in Santa Clarita and Lebec.
The blaze remains 0 per cent contained. Other evacuations to the south have been lifted.
According to the Los Angeles Times, about 100-200 homes had been evacuated, and no structures were under threat on Wednesday night.
Authorities say that the fire was initially reported near the freeway’s northbound lanes but quickly jumped across the road causing California Highway Patrol to close all lanes in both directions. Some lanes had reopened by Thursday morning.
On Wednesday, traffic on the freeway, which connects San Francisco to Los Angeles, was backed up for miles, according to KTLA.
Los Angeles County Fire Department said on Wednesday that seven firefighters had heat-related injuries on Wednesday, with five taken to hospital as they battled the fire in temperatures of more than 105 degrees. A total of eight firefighters have been reported injured.
Firefighters were seen digging containment lines in the area while the fire was also fought from the air by helicopters and airplanes dumping retardant and water on the flames.
Officials say that the cause of the fire remains under investigation.
Another blaze near San Diego, along the US-Mexico border, has burned more than 4,200 acres, injuring two people and destroying at least four structures, according to the San Diego Union-Tribune. The border crossing at Tecate, Mexico has been closed.
Southern California is currently in the grips of an extended heatwave that is expected to last until next week, with temperatures across the region hitting triple digits.
The region’s Inland Empire and desert areas are expected to see temperatures top 110 degrees Fahrenheit, while the state’s Death Valley could set a September record with a temperature of 126 degrees.
High temperatures could put stress on California’s electrical system, warned the state grid operator, as energy demands rise, largely due to air conditioning needs. Over the weekend, when temperatures are supposed to be hottest, electricity conservation may be necessary to avoid outages, they added.
In addition, extreme drought has crippled the state for years, leaving open spaces prime for burning with dry vegetation.
Wildfire risk in California and other western states is likely to get worse in the coming decades as the climate crisis grows, bringing more heatwaves and droughts that can spark and spread blazes. One recent report found that 800,000 properties in the western US were at “extreme” risk of burning in the next 30 years.