The blaze broke out Monday morning in Four Mile Canyon northwest of Boulder and rapidly spread across 5 1/2 square miles or 3,500 acres. Erratic 45-mph gusts sometimes sent the fire in two directions at once.
Despite the fire's quick and destructive advance, no injuries had been reported, although some residents told of narrow escapes.
"I just drove through a wall of flames," Tom Neur told KDVR-TV. "The bumper is melted off in the front of the van." Neur's wife, Anna, left earlier, and the couple reunited at temporary shelter. They said their house was destroyed.
"I don't care about the house," Anna Neur told her husband. "I'm just glad you're OK."
Fire managers said 1,000 homes had to be evacuated from the canyon and surrounding areas. Four belonging to firefighters were destroyed.
Those firefighters were allowed to leave to attend to their families and personal affairs, said Laura McConnell, a spokeswoman for the fire management team.
The fire's cause was unknown. Officials said it was too early to say how much, if any, of the fire was contained.
"It's very rocky, hilly, mountainous terrain," said Boulder County sheriff's Cmdr. Rick Brough.
Video from KUSA-TV showed at least one home engulfed in flames. "There is ash falling from the sky," David Jones told The Denver Post from his home in the village of Gold Hill. "We're getting out of here."
Officials said one fire vehicle was destroyed by the blaze. More than 100 firefighters were on the scene on Monday, and the winds quieted enough by late afternoon to allow three aerial tankers to begin dropping fire retardant.
Some ground crews remained at the fire through the night. At least four more aerial tankers were requested to join the fight Tuesday morning.
More than a half-dozen dirt roads that thread the narrow canyons were closed.
A billowing, white plume of heavy smoke was visible for miles before sunset. County health officials advised residents to stay indoors if the smoky air became irritating.
The Boulder County alert system malfunctioned for about two hours Monday afternoon, leaving authorities unable to send automatic calls telling residents to evacuate. Officials said it began working again later.
The Red Cross set up an overnight evacuation center at the Coors Events Center on the University of Colorado campus in Boulder.
A shelter for livestock was set up at the Boulder County Fairgrounds in Longmont.
