Officials noted that secondary containment lines are in place, beyond the primary lines, as a precaution for spot fires and in case burnouts are needed to stop them.

Fire spokesman Ken Malgren said the spot fires, kicked up by winds related to storms moving through the area, were inside a secondary containment line on the north side of the blaze, burning well away from any populated areas.

"It was on the west side of the butte, got out along Trout Creek," Malgren said.

The fire that broke out Sept. 9 six miles southwest of Sisters grew to cover over 40 square miles -- bigger than the 32-square-mile city of Bend -- though the growth has not pushed it closer than five miles from Sisters.

The cost of the battle has grown to $12.8 million, according to Tuesday's National Interagency Fire Center report.

For more of the latest information from fire officials, visit the Pole Creek Fire's InciWeb site.

Earlier information:

Air tankers returned to the skies over the fire on Tuesday for the first time in over a week, but  much of the High Desert was choked with thick smoke.

The wind shifted Wednesday, giving much of Central Oregon another look at a towering smoke plume.

Firefighters used a combination of air tankers, helicopters engines and crews to keep the fire west of Road 16 (Three Creeks Road).

The large smoke columns late Tuesday developed when the main body of the fire grew together with burnouts on the southeast corner of the fire, in efforts to secure the southern perimeter.

Firefighters remain committed to keeping the fire west of Road 16, north of Tam McArthur Rim and Triangle Hill, and south of Millican Crater, they said.

Despite all that smoke, officials stressed that all highways remain open to Sisters and other Central Oregon communities.

They also said local forest officials had authorized the use of mechanized and motorized equipment such as chain saws, water pumps and air support on both the wilderness and non-wilderness lands.

Fire managers said four air tankers were ordered up and dropped retardant on the blaze Tuesday afternoon.

They had not been part of the battle since the first day of the fire, and fire officials said that was in part due to high demand for the retardant bombers on a number of major wildfires blazing across the Northwest.

The tankers made runs Tuesday afternoon on the south end of the blaze, "mainly to reinforce the containment line of the fire," said spokeswoman Mary Ellen Fitzgerald.

"We didn't request them every day," she said, adding that the availability was checked late last Friday, the day the fire tripled in size amid hot, unstable conditions.

"The air tankers are a tool, just like helicopters," Fitzgerald said. "You select the tool that's best for the strategy you have that day."

"You also need certain conditions to be able to bring them in, be it visibility, availability -- are they around, are they on another fire?" Fitzgerald said. "We're not going to put a fire out by lining it with retardant, typically. It's a tool to help us -- it retards the fire -- and it can be a huge help," under the right conditions.

The DEQ's Wildfire Air Quality Index again showed Sisters air as "hazardous" - the worst air quality - early Tuesday while Bend's air was labeled "unhealthy for sensitive groups." Thursday morning again brought "hazardous" readings for Sisters but only "moderate" air quality in Bend.