Mayor Eric Garcetti told reporters the blaze, which broke out on Friday and lit up the hills surrounding the northern suburb of Burbank overnight, had already burnt 5,000 acres, adding: “In terms of acres involved this is probably the largest fire in LA city history.”
The blaze has so far destroyed one house and forced the evacuation of nearly 500 homes in various parts of the city and neighbouring Glendale.
More than 500 firefighters were mobilised, while 100 others who had been deployed in Houston, Texas to help rescue operations after Hurricane Harvey were asked to return.
The fire broke out on the US Labour Day holiday long weekend and as the western part of the country was facing a summer heatwave.
Authorities said wind was their main concern because it could whip up the flames and allow it to spread quickly in unpredictable directions.
A light rain sprinkled the area, but it was not enough to contain the blaze, said Los Angeles Fire Department spokeswoman Margaret Stewart.
It is 10% contained.
The region was under a red flag warning from the National Weather Service until at least today morning as temperatures were expected to climb above 37.8 degrees Celsius with strong winds and low humidity.
Video posted online by local media showed the fire burning along the 210 Freeway, with smoke hovering over the roadway as cars passed by flames.
Officials quickly closed a section of the freeway, which remained shut down yesterday.
More than 640km to the north, the so-called Ponderosa Fire has burned 3,880 acres and destroyed 30 homes in Butte County since it broke out on Tuesday.
It prompted authorities to issue evacuation orders earlier this week to residents of some 500 homes.
The blaze, which grew from a campfire that was started outside a designated area, was 45% contained, officials said.
California Governor Jerry Brown issued an emergency declaration on Friday to free up additional resources to battle the blaze.
The man charged with starting the fire, John Ballenger, made his first court appearance in Butte County Superior Court on Friday, District Attorney Michael Ramsey said.
Ballenger was charged with two counts of arson and was ordered held on a $1mn bond.
In Montana, Governor Steve Bullock declared a state of disaster on Friday due to wildfires as dozens raged across tens of thousands of acres during one of the worst fire seasons in state history.
