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SUN VALLEY (CBSLA.com) – A massive brush fire burning downhill in the Sun Valley and Burbank area Saturday is being called the biggest fire by acreage in the history of the city of Los Angeles.

The La Tuna Fire was just 10 percent contained Saturday night, and has already consumed more than 5,800 acres. The fire spread into Burbank overnight and was active on both sides of the 210 Freeway, which was shut down in both directions between the 118 and 2 freeways. Firefighters were battling triple-digit heat and unpredictable winds for the second consecutive day.

Mandatory and voluntary evacuation orders had been issued for 730 homes: 300 in Burbank, 250 in Glendale and 180 in the city of L.A. Evacuation orders for Burbank were lifted around 10 p.m. Fire officials urged residents in the affected areas to be prepared to leave immediately if more evacuations orders are given, however.

The Los Angeles Fire Department confirmed that two homes were destroyed Saturday, including a home near a water tank at Verdugo Crestline and Alene drives in Tujunga. There have been no reported injuries so far.

#LaTunaFire General burn area of fire +5,000 acres 10% contained 1 house lost Detailed evac map pending List here https://t.co/YrRAiGk9Tv pic.twitter.com/KduKAoUzdJ — LAFD (@LAFD) September 2, 2017

LAFD said the fire is a slow burning “backing” fire, meaning that it is burning downhill. Crews have set up resources at the base of hills to defend homes. Erratic winds are the greatest threat to the firefight.

“The biggest factor is weather and the wind,” LAFD Battalion Chief Ralph Terrazas said during a news conference at the department’s command post in the parking lot of the Hanson Dam at Osborne Street and Foothill Boulevard. “If there is no wind, this fire is relatively easy to put out. The wind changes, it changes our priorities.”

The blaze broke out for unknown reasons at 1:25 p.m. Friday near the 10800 block of La Tuna Canyon Road, just south of the 210 Freeway. About a half-acre of medium brush was on fire when the first crews arrived Friday afternoon. Wind-blown embers sparked a spot fire on the north side of the freeway, and by 4 p.m. Friday, firefighters were battling flames on both sides of the freeway as the fire raced up a hillside of the Verdugo Mountains in the direction of Burbank.

Authorities began calling for mandatory evacuations at 10:30 p.m. Friday for the Brace Canyon Park area of Burbank when the fire jumped the ridgeline and when firefighters performed structure defense operations to protect homes in the area.

“The wind, Friday afternoon, was very erratic. It switched multiple times,” said Terrazas, adding that there have been no firefighter injuries. “We’re constantly evaluating and it’s dependent upon the wind shifts. Our priority is saving property. We’re evaluating that at all points of the fire. Five thousand acres is significant. Like the mayor said, the last fire (like this) was 30 to 40 years ago. So there’s a lot of fuel to burn.”

He also advised all homeowners in the area to clear any brush on their properties to give firefighters a better chance at savings their homes.

About 500 firefighters are working on the blaze now, additional resources have been requested from the state, and about 100 L.A. firefighters are expected back from Texas soon, where they’ve been helping survivors from Hurricane Harvey, officials said. Four fixed-wing airtankers have been ordered to fight the blaze as well.

Los Angeles Mayor Eric Garcetti on Saturday evening declared a local emergency.

“The La Tuna Canyon Fire is an emergency that requires all available resources to protect our residents and keep our homes and other structures out of harm’s way. We are grateful for the men and women of LAFD, and all our partner agencies, for their heroic efforts to attempt to bring the fire under control and to keep people and their homes safe,” Garcetti said in a statement. “I have signed a Declaration of Local Emergency that directs relevant departments in the City of Los Angeles to take all necessary steps to protect life and property in the area affected by the fire. This declaration also requests that the Governor declare an emergency — so that state and federal assistance can be provided to the City as quickly as possible.”

“We are worried about the fire hooking, of course, into the southeast, into Glendale and working its way up from there,” Garcetti said. “We have firefighters confining this (brush fire) as it goes.”

In Tujunga, mandatory evacuations are in place in the McGroarty Park area (McGroarty to Valaho), while voluntary evacuations have been urged for Aileen and Hillhaven, McGroarty from Oro Vista to Plainview, Alene Drive to Hillhaven Avenue, Reverier, Glen O Peace Parkway, Tranquil Drive, Inspiration Way, Tranquil Place, Hillhaven Place and the Haines Canyon Area.

In Sunland, voluntary evacuations have been urged for Shadow Island Drive and Wormom Avenue South of Sunland Boulevard.

Burbank residents living on Amigos Drive or Antigua Drive have been told they may return home.

Mandatory evacuations were issued for the Glendale communities of Glenwood Oaks and Mountain Oaks at 11 a.m. Saturday due to the risk of a power outage.

Evacuation centers are in place in Burbank at McCambridge Park, 1515 Glenoaks Blvd.; in Sunland at Sunland Recreation Center, 8651 Foothill Blvd.; in Glendale at the Civic Auditorium, 1401 N. Verdugo Road; and in La Crescenta at Crescenta Valley High School, 2900 Community Ave.

Pets are being welcomed at all the evacuation centers, and officials caution that animals should not be left behind.

“I want to say this loud and clear that folks who leave their homes, we have police assets who will stay in the neighborhood,” Garcetti said. “Do not be nervous of anybody who would take advantage of a tragedy like this and try to get into those neighborhoods, you will be caught.”

“What we see is a fire that we can contain ultimately,” he said.

Firefighters used night-vision goggles to make overnight water drops on the blaze, said Margaret Stewart said of the Los Angeles Fire Department.

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