BOISE - 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 had grown by only about 12 square miles because of cloud cover the day before and the arrival of additional crews and equipment. Many firefighters worked Sunday to create protective firebreaks, or gaps in vegetation.

"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 were battling the lightning-caused Beaver Creek Fire, which started Aug. 7 and was 9 percent contained. Nearly 90 fire engines also were in the region, many protecting homes in the affluent area where celebrities like Arnold Schwarzenegger, Tom Hanks and Bruce Willis own pricey getaways.

Hartman said Sunday retardant was being dropped on the flank of Bald Mountain - the Sun Valley Resort's primary ski hill - to reinforce a fire line. That meant the famed ski mountain known as "Baldy" and often used in publicity photos would 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, but he noted the fire had not yet spread to the mountain.

Meanwhile, crews continued battling other wildfires across the West, including a group of fires near the Oregon city of The Dalles, on the Columbia River.

Those fires were threatening about 70 homes Sunday, and some residents in the area were told to be ready to evacuate. The state fire marshal's office said there was fire about a mile and a half from some structures.

Three wildfires were burning in the area, with the largest covering about 700 acres in The Dalles watershed. The lightning-caused fires were detected Friday. About 200 people were assigned to help combat them.

In Idaho, fire managers said both of the nation's DC-10 retardant bombers have been used to battle the Beaver Creek 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 was on the south and west sides. The more populated areas are on its eastern side and are where the mandatory evacuations were in place.

No structures have been destroyed since a house and outbuildings burned Thursday, officials said. On the fire line, a few minor injuries were reported.