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The Bobcat Fire crossed into Monrovia city limits as it continued to burn for a sixth day Friday in the Angeles National Forest. But the blaze did not grow in acreage or containment, officials said.

The flames breaches the northern edge of Monrovia but were kept north of Monrovia Canyon Park and above residential neighborhoods, as crews continued working to defend the area, the city of Monrovia said around 1:30 p.m.

“Firefighting crews have spent a considerable amount of time building defensive lines on the western and southern edges of the fire, which is located directly above Monrovia,” officials wrote.

Blackhawk helicopters were also being used to patrol the southwest perimeter of the wildfire, where crews are focusing containment efforts to protect homes.

The communities of Monrovia, Arcadia, Bradbury, Sierra Madre, Altadena, Duarte and Pasadena remain under an evacuation warning.

The public was asked to avoid going into areas above Foothill Boulevard. Thursday night, evacuation routes became clogged with people trying to take photos of flames, officials said.

The wildfire, which began Sunday, had scorched 26,368 acres and was 6% contained as of Friday night, according to the U.S. Forest Service.

The containment line has been established where the blaze ran into the burn scar from last month’s Ranch 2 Fire, and the eastern and western flanks are also coming up against land previously charred by the 2016 Fish Fire and 2009 Station Fire.

But the blaze remained active Friday on its northern perimeter, where there is no fire history in the last 80 years, officials said. Firefighters were monitoring for flares up in the area and working to keep flames north of Highway 39.

The heavy smoke choking the region actually helped slow the flames’ spread by keeping temperatures down, crews said.

Overnight, firefighters planned to focus on keeping the fire from growing around Angeles Crest Highway and Highway 39, as well as protecting homes south of the blaze.

Gusty winds died down Thursday, allowing fire crews to work on building a perimeter. On Thursday night, there was fire activity in the area of Rankin Peak, going down to Monrovia Canyon and up to Clamshell Peak. The fire also burned in the drainage up to Kratka Ridge, up to Angeles Crest Highway and up to Highway 39, according to Kerri Gilliland, planning operations trainee of the California Incident Management Team 1.

More than 500 firefighters are still battling the blaze.

During Friday’s update, Gilliland said fire crews were also working on opening dozer lines and using the road system to slow progression of the fire.

“Local fire department will continue to conduct structure protection planning and triage efforts within the foothill communities,” officials stated.

More activity is expected on the north side, where crews will work to contain the fire at Angeles Crest Highway.

Heavy fuel for the fire, some of which hasn’t burned in the last 60 years, is expected to push the fire into another old burn scar in the west.

Residents should be ready to leave immediately if officials decide to issue an evacuation order.

Highway 39 remains closed at Old San Gabriel Canyon Road, while the Angeles Crest Highway is closed from about 10 miles east of La Cañada Flintridge to Islip Saddle. Crews were also working Friday to try and contain the fire to the west of Highway 39, Gilliland said.

Smoke from the fire is creating unhealthy air across Southern California. Residents were asked to avoid any unnecessary outdoor activity if smoke or ash is in the air.

The cause of the fire is unknown.

All 18 National Forests, including the Angeles National Forest, are under a closure order. All general activity is prohibited.