U.S. Forest Service crews stopped the forward progress of a brush fire burning in a dense, forested area of the San Gabriel Mountains north of Glendora on Sunday.

By late afternoon, fire crews were working to contain the blaze. Containment on the fire remained at 0 percent by 5:20 p.m., forest officials said.

Multiple air tankers were requested to help douse the fire first reported burning near the intersection of Highway 39 and Fork Road, near the northwest spur of the San Gabriel Reservoir, according to officials from an inter-agency group of Angeles National Forest and fire officials.

ANF assisted by @LACOFD working the #ForkFire in San Gabriel Canyon, Highway 39 at the East Fork Road. 60 acres 0% contained. Evacuation of recreational visitors continues, HWY 39 closed two miles above Sierra Madre Blvd. pic.twitter.com/TfhB1Bmo8V — Angeles_NF (@Angeles_NF) September 9, 2018

The blaze, dubbed the “Fork” fire, was burning heavy vegetation in steep terrain, according to USFS images posted to Twitter. The fire was located about nine miles north of Glendora, near recreational areas of the San Gabriel Mountains National Monument.

Forest Service crews first reported a 50-acre fire rapidly spreading at around 12:30 p.m. Multiple firefighting hand crews and strike teams were called to the area, and firefighting aircraft were requested from around the region and Northern California.

On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

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On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG



On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

On Sunday, Sept. 9, 2018, L.A. County firefighters and U.S. Forest Service firefighters responded to a brushfire at Highway 39 and East Fork Road. Photos by Rick McClure/Special to the Los Angeles Daily News/SCNG

One report from a Los Angeles County Sheriff’s Department official said the fire had reached 70 acres, but by 5:20 p.m. forest officials said the fire had only grown to 60 acres.

While the fire had only burned a relatively small area, the intensity of the flames, fueled by the heavy brush and trees in the area, was hot enough to be seen from space — National Weather Service officials said on Twitter that the heat signature of the fire was picked up by satellites.

Satellite imagery is picking up some heat signatures due to an apparent new fire near Hwy 39 south of Falling Springs. Unknown fire name @NWSLosAngeles #CAwx pic.twitter.com/j0pg7vv3QZ — NWS San Diego (@NWSSanDiego) September 9, 2018

The smoke plume was visible throughout the San Gabriel Valley and beyond, according to residents posting photos to social media.

View from glendora 7 minutes ago pic.twitter.com/JsnIVxzbjz — Nelson Smith (@nelsonsmith64) September 9, 2018

The fire shut down Highway 39 in San Gabriel Canyon about two miles north of Sierra Madre Boulevard and the highway will remain closed at least through Monday morning, USFS spokesman Nathan Judy said.

No structures were threatened, but campers and people using the popular swimming holes in San Gabriel Canyon were evacuated Sunday. Park visitors north of the fire were stuck, their only normal exit from the park cut off to the south, Judy said.

They were escorted out via a closed section of Route 39 to the Angeles Crest Highway, across a treacherous roadway subject to rockfalls that is usually closed to the public.

Judy said one firefighter sustained a minor injury when a rock rolled down a hill and struck him in the leg. He was treated with the assistance of the Los Angeles County Sheriff’s Department’s Air Rescue 5 helicopter crew.

Judy estimated there were between 150 and 200 firefighters battling the brush fire.

VIDEO: #LASD Air Rescue 5 hovers over #ForkFire while rescuing an injured firefighter, victim of rockfall. LASD SEB Tactical Medics hoist firefighter into the aircraft and transport him to trauma center. Public safety #teamwork. pic.twitter.com/JU2pQ9tiZ0 — SEB (@SEBLASD) September 10, 2018

L.A. County firefighters sent one water-dropping helicopter, a bulldozer and about 30 personnel to assist USFS personnel fighting the blaze, a dispatcher said.

A giant aerial tanker from Sacramento was being flown to assist the Forest Service and Los Angeles County firefighters.

Tanker 911 is a jumbo DC-10 jet converted to fire tanker purposes.