On their fourth day of battling the Canyon Fire in the hills above a Corona neighborhood, firefighters have increased containment to 60 percent, officials said Thursday evening.

While the fire didn’t grow or burn any additional structures on Thursday, firefighters were able to make a better assessment of its damage.

Officials used GPS mapping to determine it has burned 2,662 acres in the foothills south of the 91 Freeway between Corona and Anaheim, up from the previous estimate of 2,000 acres.

And after walking through neighborhoods and checking backyards, firefighters discovered three more damaged structures, for a total of six, said Orange County Fire Authority Capt. Larry Kurtz. Four of those structures are houses, one is a commercial building and one is an outbuilding. No structures were a total loss, he said.

“Firefighters are continuing to build and reinforce fire line, mop up hot spots and patrol the fire perimeter,” according to a news release from the Orange County Fire Authority.

Full containment remains projected for Sunday, Oct. 1.

Officials are asking the public to avoid recreation use of Skyline Drive through the weekend due to heavy equipment working in the area.

About 1,900 firefighters had been assigned to the fire at one point, but in the Thursday evening report, that number has decreased to 1,453. The air resources also have been reduced from about 20 helicopters and air tankers to just two helicopters.

The fire ignited Monday afternoon off the eastbound freeway just west of the Green River Road exit. The cause remains under investigation. Winds fanned it toward Corona on Monday night, leading to the evacuation of about 600 homes that butted up against the burning hillside.

The evacuation order was lifted Wednesday morning, allowing grateful residents to return home.

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