The Bobcat Fire, one of the largest fires in Los Angeles County history, had grown by midweek to an excess of 109,300 acres. County fire officials report that containment had increased to just over 50 percent by Thursday morning.

The fire, which is burning in the Angeles National Forest (ANF) and threatening communities in the Antelope Valley and San Gabriel Valley foothills, has destroyed or damaged 29 structures, with authorities fearing the number could rise to 85.

“Crews, aircraft and equipment worked through the evening picking up (hot) spots and securing the lines,’’ the Angeles National Forest said in a statement Tuesday morning.

The fire has burned more acres than the Woolsey Fire of 2018, which burned 96,271 acres, the Los Angeles County Fire Department said Tuesday. The Station Fire in 2009 burned 160,577 acres.

The fire came down from the Angeles National Forest into the communities of Cima Mesa, Juniper Hills, Pearblossom, and Devil’s Punchbowl on Sept. 18 and damaged some structures, the LACFD’s Vince Pena said Monday evening. “We’re still currently aggressively assessing the damage from that,’’ he said.

The Nature Center at the Devil’s Punchbowl Natural Area was burned by the fire, Los Angeles County parks officials said. The area is closed until further notice.

“Firefighters will focus on the SW and NE corners of the #BobcatFire today,’’ the ANF tweeted at about 9 a.m. Tuesday. “Expect to see smoke plumes and aircraft north of Mt. Wilson as crews engage in strategic firing operations.’’

The U.S. Forest Service reported Tuesday afternoon that the defensive firing operation was “going well at Mt. Wilson. They’re using aerial ignitions to increase the buffer between HWY 2 near Barley Flat to Big Tujunga Road.’’

The blaze advanced on Mount Wilson on Monday while prompting fresh evacuation orders as officials worked to prevent the flames from spreading out of the Antelope Valley foothills.

A smoke advisory was extended through Wednesday warning of unhealthy air in the San Gabriel Mountains, and for sensitive individuals in the San Gabriel, Santa Clarita and Antelope valleys.