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Firefighters deployed to protect the Mount Wilson Observatory from the Bobcat Fire in the Angeles National Forest are “ready to receive the fire,” officials said Tuesday afternoon.

Observatory officials earlier said the boundaries were still secure. But by 12:31 p.m., Angeles National Forest officials said that the flames were within 500 feet of the 116-year-old observatory.

“There’s major infrastructure for radio, television and cell towers up there, so there might be possible disruptions.” L.A. County Fire Capt. David Dantic told the L.A. Times.

Crews were trying to suppress a spot fire about 500 to 1,000 acres that has jumped Highway 2, or the Angeles Crest Highway, officials said.

They had worked overnight to protect the observatory as well as the foothill communities, above which the blaze remained active Tuesday evening as it grew to about 41,770 acres.

Officials increased their resources in an effort to reduce the fire’s growth. More than 1,150 firefighting personnel are now battling the blaze, the U.S. Forest Service stated.

Additional resources and fire crews arrived over the past three days, officials said.

The Bobcat Fire, which started on Sept. 6, was 3% contained as of Tuesday night, according to the Forest Service’s information website.

Smoky skies and marine layer fog have made it difficult for pilots to assist ground crews during the morning hours, Dantic previously told KTLA.

“Our biggest concern is safety for our pilots. If they’re not able to see where they’re going, it makes it impossible for them to fly,” Dantic said.

A smoke advisory from the South Coast Air Quality Management District is in effect through at least Wednesday.

Tuesday’s primary focus was to protect the foothill communities to the south of the fire and the Mount Wilson area, officials stated.

The second priority had been to keep the northern end of the fire south of Highway 2, north of which crews continued to fight a spot fire Tuesday night.

Evacuation orders are in place for parts of Sierra Madre and Arcadia, including areas located north of Elkins Avenue and east of Santa Anita Avenue. San Gabriel Canyon also remains under an evacuation order.

A fire information map posted by the U.S. Forest Service is seen on Sept. 15, 2020.

A Red Cross evacuation center is open at 285 W. Huntington Drive in Arcadia. Residents should enter through Gate 5.

Residents north of Foothill Boulevard and east of Santa Anita Avenue remain under an evacuation warning. Also, the foothill communities of Monrovia, Bradbury, Sierra Madre, Altadena, Duarte and Pasadena should be prepared to evacuate if needed.

Officials have extended the closure of the Angeles National Forest along with the rest of the state’s national forests through Sept. 21.

Investigators have not yet determined a cause for the Bobcat Fire.