Evacuations were ordered in areas of Colorado and New Mexico where wind-fanned wildfires quickly spread Saturday -- including one fire that burned through 10,000 acres in one day.
In Colorado, a fire 15 miles of west of Fort Collins grew from 200 acres on Saturday morning to 5,000 acres by 7:30 p.m. MDT, the fire incident command reported. Plumes of black smoke could be seen from the Denver metropolitan area.
Evacuations were ordered for some 40 homes in several communities.
Fire spokeswoman Jennifer Hillman told Reuters that authorities have been unable to locate or make contact with a number of people who live in the area.
The cause of the fire was still unknown.
"This is the fire we always feared we'd have," Larimer County Sheriff Justin Smith said at an 8 p.m. press conference, the Denver Post reported.
In New Mexico, a lightning-sparked fire that started Friday had grown to 10,000 acres, fanned by 20 mph winds. Crews were dealing with flames 150 feet high at times.
Burning 15 miles north of Ruidoso, where heavy smoke hung in the air, the fire crossed Highway 48 and destroyed or damaged up to 20 structures, the fire incident command reported.
Campgrounds and communities were evacuated in the immediate area.
"It's nowhere near controlled. We're doing a lot of evacuations," Lincoln County Undersheriff Robert Shepperd was quoted by the Alamogordo Daily News as saying.
Some 350 more crew were expected to be on the firelines on Sunday.
"It's nerve-racking right now," Ruidoso Mayor Ray Alborn told the newspaper, adding that "real heavy smoke" was rising from the Sierra Blanca mountain range.
"Today all we see is smoke," he said. "Last night, we saw the flames too and it was an awesome expression of power. It was red, red and we could see it going across the top."
New Mexico is also still dealing with its largest wildfire on record, a massive 275,000 acre blaze in the Gila National Forest.
The 826 firefighters there were also battling high winds, but have been able to bring containment to 32 percent after a month of efforts.