The fire broke out and began burning on a hill around 1:30 a.m. adjacent to the 405 Freeway at Getty Center Drive near the Getty Center museum.
It quickly exploded to 618 acres by noon.
By Monday evening, officials said the good news was the fire had not increased in size and it was estimated at 5% containment.
"It remains where it is in place with amazing muscle and work coming from our fire crews that are out there right now," Mayor Eric Garcetti said.
Most of the evacuations that were ordered throughout the day Monday were expected to stay in place overnight and possibly through Tuesday night. The exception was the Mountaingate community located south of Mulholland and north of the burn area, which was changed to a voluntary evacuation meaning residents could return if they chose.
"You should be prepared for two nights at least that the majority of folks will be out of their homes," Garcetti said.
Los Angeles Unified School District campuses in the area were also expected to remain closed Tuesday.
There were more than 1,100 fire personnel fighting the blaze.
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The California Highway Patrol said homes in the area were being threatened and the southbound side from the 101 Freeway to Sunset Boulevard was shut down, as well as all off-ramps on the northbound side between Sunset Boulevard and Mulholland Drive.
The 405 Freeway was shut down in the area but authorities were expected to reopen it Monday evening.
The Getty Center museum was not believed to be in danger from the flames, officials said.
MORE: See full list and map of evacuation area, road closures due to the Getty Fire
L.A. Mayor Eric Garcetti announced he was signing an emergency declaration to bring more resources to help battle the blaze. During a press conference, Garcetti said the fire was not caused by an encampment or by someone without housing.
"There's an active arson investigation. I would also say to the public, when you hear arson, you think that somebody has set it. Arson investigations are just the cause of the fire, that doesn't necessarily mean somebody has set it. Some thing can set that as well," Garcetti said.
The mayor said investigators were making "good progress'' in determining the cause. They were looking at multiple possibilities.
LAFD arson investigators were with Los Angeles Department of Water and Power crews inspecting a power pole along Sepulveda Boulevard in the general area where the blaze started. LAFD Chief Ralph Terrazas confirmed that crews have identified the fire's point of origin just off the 405 Freeway near Sepulveda Boulevard.
Investigators were also looking at a broken tree branch with a charred end that was on the ground along Sepulveda just south of the Skirball on the west side. The branch was set aside on the ground surrounded by cones.
At least eight homes appeared to be destroyed by the flames, many of them on North Tigertail Road. At least five more were incurring damage as they burned along the 1100 block of North Tigertail.
PHOTOS: Getty Fire burns in West Los Angeles
"We still have about five structures we believe here that the fire has taken, a couple across the canyon as well," Garcetti said about the homes on N. Tigertail Road.
Mandatory evacuations were issued for the MountainGate and Mandeville Canyon communities as early as 2:40 a.m. The freeway remained opened to allow evacuees to leave the area. Mountaingate was allowed to repopulate by 5 p.m.
The mandatory evacuation zone was later extended to the west, with Temescal Canyon Road established as the western border, and Sunset Boulevard as the southern border, according to the Los Angeles Fire Department. Mulholland Drive is acting as northern border and the 405 Freeway remaining the eastern border.
Garcetti urged residents to immediately heed evacuation orders.
"I tell everybody if you get this order, don't be a hero, don't fight it on your own," Garcetti said in an interview with Eyewitness News. "Don't take your garden hose out. Get out. Bring your kids, your pets, your valuables if you have time. Get out. That's the only thing you can't replace - your life."
LAFD officials said about 10,000 residential and commercial structures were under mandatory evacuation as the fire moved westward.
On Twitter, Los Angeles Lakers star LeBron James said he had to evacuate his home. Former California Gov. Arnold Schwarzenegger was also among those who were evacuated. Mayor Garcetti said his parents had also been evacuated from their home.
RELATED: Lebron James, Arnold Schwarzenegger among the thousands forced to evacuate due to Getty Fire
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The Chalon campus at Mount Saint Mary's University was also being evacuated, with students sent to the Doheny Campus. Several evacuation centers were available to those evacuated.
About 2,600 customers were without power due to the blaze, according to the Los Angeles Department of Water and Power. The affected area included Bel Air, Brentwood and Westwood. It is unclear when power will be restored.
About 500 firefighters were tackling the blaze from the air and ground.
RELATED: How to help Los Angeles firefighters responding to devastating fires in Southern California
An emergency alert message was sent around 2:45 a.m. notifying residents of the need to evacuate due to the blaze.
Southern California is bracing for the return of Santa Ana winds as it remains under red flag conditions Monday. Several blazes ravaged the area last week as the combination of Santa Ana winds, low humidity and hot temperatures created dangerous fire conditions.
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