(LOS ANGELES) — More than 8,600 firefighters simultaneously battling three major Southern California wildfires made substantial progress overnight, taking advantage of cooler and wetter weather to increase containment lines on all three blazes, authorities said Sunday.

The largest blaze — the Bridge Fire burning in Los Angeles and San Bernardino counties — was at 54,567 acres as of Sunday morning, according to the California Department of Forestry and Fire Protection (Cal Fire).

More than 2,600 emergency personnel battling the fire increased containment to 9% on Sunday, up from 2% on Saturday morning. Fire crews ensured a “minimal” spread of the inferno by about 800 acres overnight, according to Cal Fire.

Two firefighters have been injured in the Bridge Fire, which began on Sept. 8. At least 19 structures have been destroyed and six damaged, with 11,560 more still under threat, Cal Fire said.

The northwest corner of the fire was most active through Saturday, Cal Fire added, while the east side of the blaze still poses risks to residents in the Mount Baldy area, where evacuation orders remain in effect.

Firefighters held their containment line on its south side in the Sunset Peak area, and increased containment there by 2%.

The cause of the Bridge Fire remains under investigation.

Elsewhere in the Los Angeles area, firefighters were gaining the upper hand on two other major wildland blazes.

Line Fire

Firefighters in San Bernardino County increased containment of the Line Fire to 36% on Sunday morning, up from 25% to 29% on Saturday, according to Cal Fire. The blaze, which was started Sept. 5 by an alleged arsonist, was 38,421 acres in size as of Cal Fire’s latest update Sunday morning.

Some 36,300 structures are being threatened, with one destroyed and three damaged as of Sunday. There are 4,103 fire personnel fighting the blaze, with three firefighters so far injured.

“Late Friday night and into the early hours Saturday, Line Fire activity was moderated due to higher moisture levels,” San Bernardino National Forest officials said, though they added that danger of spreading fire remained in dry vegetation, drainages and along slopes.

“The weather is expected to remain cool over the next several days which will continue to help moderate fire behavior,” the national forest officials said.

Airport Fire

Firefighters battling the Airport Fire in Orange and Riverside counties grew containment from 9% to 19% on Saturday, Cal Fire reported, with the fire now 23,519 acres in size.

The wildfire destroyed 109 structures and damaged 24 more as of Saturday night, Cal Fire said, with another 21,993 still threatened. Fourteen people — 12 firefighters and two civilians — have been injured.

“Favorable weather conditions persisted, with the marine layer returning this evening and forecast light precipitation in the coming days,” Cal Fire wrote on Saturday evening.

“Despite recent weather, the dry vegetation has exhibited active fire behavior, indicating the continued risk of increased fire activity,” Cal Fire said.

“Evacuation levels are being assessed daily by fire managers in collaboration with law enforcement based on fire containment and safety considerations,” it added. “Efforts are underway to safely return residents to their homes as conditions permit.”

The Airport Fire began around 1 p.m. PT on Tuesday, sparked by county public works crews working on a fire prevention project by trying to move boulders to prevent public access — mostly by motorcyclists — to an area of the canyon with a lot of dry vegetation that could ignite easily, officials told Los Angeles ABC station KABC.

ABC News’ Samira Said and Tristan Maglunog contributed to this report.

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