A shift in winds helped firefighters battle a 2,500-acre wildfire, but officials feared the arrival of warmer temperatures could slow the fight.

Winds shifted Thursday and blew the flames back into previously charred areas, helping crews get containment lines around 35 percent of the fire. Cooler temperatures and higher humidity also aided the effort.

Temperatures reached into the 30s overnight but were forecast to climb to the high 50s or low 60s on Friday.

The National Weather Service said there was a chance of mountain snowfall Friday night and Saturday, but the weather was expected to dry out again by Sunday.

Officials had expected to get only 20 percent containment of the fire Thursday.

"We did better than expected. There's still a threat to structures, but we'll keep working it," U.S. Forest Service spokesman Steve Segin said.

More than 600 firefighters and 85 trucks were on the scene 35 miles southwest of Denver. Some were expected to be sent home Friday.

The fire forced the evacuation of 250 houses in Bailey, a town of 4,400 people about 35 miles southwest of Denver, when flames crept to within a quarter-mile of downtown. Three schools were closed Thursday.

Authorities were questioning three high school freshmen who were seen running from a ridge where the fire started Tuesday. Smokers often congregate there, officials said.

The teens' parents were cooperating, Park County Sheriff Fred Wegener said. Two of the families have hired lawyers.

The fire was burning just a few miles north of an area where 10,800 wooded acres burned and 51 homes were destroyed in 2000.

This year, a winter drought has plagued much of the West, triggering an early start to the wildfire season.

In central New Mexico, firefighters contained a 300-acre fire in the Magdalena Mountains and were trying to snuff out hot spots early Friday. In Arizona, a 1,120-acre fire in the Baboquivari Wilderness about 45 miles southwest of Tucson was 90 percent contained.

The Bureau of Land Management and Forest Service have imposed fire bans on parts of Colorado, on top of restrictions announced by about a third of the state's 64 counties.

Starting Friday, open fires were also banned at Rocky Mountain National Park in northern Colorado.