Pacific Palisades resident Mike Sutton, 31, and his son, Tommy, 2, watch the deployment of firefighters at the Palisades Fire in the Pacific Palisades area of Los Angeles, Sunday, May 16, 2021.Ringo H.W. Chiu/AP

Amy Graff, SFGATEMay 17, 2021Updated: May 17, 2021 11:14 a.m.

LATEST May 17, 11 a.m. More than 500 homes — many of them mansions worth millions of dollars — remain threatened in Topanga Canyon as a smoky wildfire churns in the dry brush of the Santa Monica Mountains, the Los Angeles Fire Department said in a Monday press conference.

The department said the so-called Palisades Fire stands at 1,325 acres and there is no containment as of Monday morning. New numbers are expected to be released later Monday.Firefighters are on the ground battling flames in steep, rugged terrain, and air tankers and helicopters are dropping water and fire retardant over remote area

This is very challenging terrain,” a spokesperson from the department said in the press conference. “It has been about 75 years since we’ve had a fire in this area. Some of the brush is 20 to 30 feet high.”

The fire is burning about 18 miles west of Los Angeles. 

May 17, 7:30 a.m. A wildfire burning in the parched brush of the Santa Monica Mountains grew to 1,325 acres overnight, while about a thousand residents remained under mandatory evacuation orders and others prepared to leave under a warning, authorities said. There is no containment, as of Monday morning. 

The blaze that the Los Angeles County Fire Department has named the Palisades Fire sparked at 10 p.m. Friday near Topanga State Park in the mountains behind the community of Pacific Palisades. It smoldered for much of Saturday before erupting in the afternoon and flaring up again Sunday.

“We’re trying to keep it up out of the old growth, which is 50-60 years [old] that hasn’t burned,” Los Angeles City Fire Public Information Officer David Ortiz said Sunday, according to ABC 7. “So there’s a lot of dense, thick material there — oily plants that have died out because of the drought. So that’s our objective today is to try to keep it out of that and protect the communities and neighborhoods to the west of this fire because that’s what’s closest to it.”

Los Angeles City Fire Public Information Officer David Ortiz told ABC 7 that firefighters are trying to keep the blaze out of an area that hasn’t burned in 50 to 60 years. “So there’s a lot of dense, thick material there — oily plants that have died out because of the drought,” Ortiz said on Sunday. “So that’s our objective today is to try to keep it out of that and protect the communities and neighborhoods to the west of this fire because that’s what’s closest to it.”

The cause of the fire has been deemed “suspicious” and is under investigation, the fire department said.

Arson investigators with the fire department and the Los Angeles Police Department identified one individual who was detained and released. Investigators then detained a second suspect and were questioning them Sunday evening, according to a statement from fire department spokesperson Margaret Stewart.

Cool, moist weather early Sunday gave firefighters a break, but by the afternoon flames starting moving again in steep terrain where tinder-dry vegetation hasn’t burned in a half-century, the fire department said.

“We’re definitely seeing increased fire activity,” said Stewart.

As of Monday morning, no structures were damaged and no injuries were reported.

An update is expected from the fire department at 10 a.m. Monday. A live stream is available on the department’s Facebook page.

On Sunday night, the department said evacuation orders would remain in effect overnight with about a thousand residents of the Topanga Canyon area fleeing their homes. The order is in effect for residents located east of Topanga Canyon Boulevard between Topanga Community Center and Viewridge Road, as well as those north of Entrada Road, south of Oakwood Drive and east of Henry Ridge Mountain Way. An area of Michael Lane is under an evacuation warning

Los Angeles has seen very little rain in recent months, making for extremely parched conditions and high fire risk.

Crews relied on aircraft making drops of water and retardant because “the terrain is very steep and extremely difficult to navigate which hinders ground based firefighting operations,” a fire department statement said.

Topanga Canyon is a remote, wooded community with some ranch homes about 20 miles (32 kilometers) west of downtown Los Angeles, on the border with Malibu.

The Associated Press contributed to this report.