Fire managers expressed optimism Sunday in their battle against a wildfire that has scorched nearly 160 square miles and forced the evacuation of 2,300 homes near the central Idaho resort communities of Ketchum and Sun Valley.

Officials said the blaze only grew about 12 square miles because of cloud cover Saturday and the arrival of additional crews and equipment. Many firefighters worked Sunday putting in protective fire breaks.

“Today they’re very optimistic that we will reinforce those lines in case the fire does flare up as we saw on Thursday and Friday,” fire spokeswoman Shawna Hartman said.

More than 1,200 people and 19 aircraft are now battling the lightning-caused Beaver Creek Fire, which started Aug. 7 and is 9 percent contained. Nearly 90 fire engines also are in the region, many protecting homes in the affluent area where celebrities like Arnold Schwarzenegger, Tom Hanks and Bruce Willis own pricey getaways.

Fire managers said both of the nation’s DC-10 retardant bombers have been used to battle the fire, but one experienced an engine malfunction after a drop Thursday. The jet made it back safely to Pocatello in southeastern Idaho but remains unavailable.

Hartman said most of the fire’s containment is on the south and west sides. The more populated areas are on the eastern side of the blaze and are where the mandatory evacuations are in place.

Blaine County spokeswoman Bronwyn Nickel said Idaho National Guard soldiers are manning checkpoints at evacuated neighborhoods and helping relieve local law enforcement officers. The Blaine County Sheriff’s Office is warning evacuated residents not to return until notified it’s safe to do so.

Officials say no structures have been destroyed since a house and outbuildings burned Thursday. On the fire line, a few minor injuries have been reported.

Authorities have told Ketchum and Sun Valley residents to be ready to evacuate if necessary. About 2,700 people live in Ketchum, 1,400 in Sun Valley.

Hartman said retardant was being dropped on the flank of Bald Mountain — the Sun Valley Resort’s primary ski hill — to reinforce a fire line. That means the famed ski mountain known as “Baldy” and often used in publicity photos will have a red line of retardant visible from Ketchum.

Hartman said the drop was part of a plan by fire managers to bolster protection for the tony resort town.

Elsewhere in the West, the last evacuation orders were scheduled to be lifted today after a series of mountain fires burned more than a dozen homes in Utah.

More than 100 residents who were forced to leave two communities about 45 miles east of Salt Lake City will be allowed to return in the morning.

Fire officials said Sunday the nearly 2,000-acre Rockport fire near the resort town of Park City was 70 percent contained.

Utah’s biggest blaze, the Patch Springs Fire, was estimated at 50 square miles and 25 percent contained Sunday.

No evacuation orders remained for that fire, which burned 10 homes near Willow Springs on Friday, but a portion of State Highway 199 remained closed.