A wind-driven wildfire broke out in the rugged Colorado foothills and quickly spread across 14 square kilometres Monday, destroying some buildings and triggering the evacuations of as many as 1,000 homes.

The fire started in Four Mile Canyon northwest of Boulder and erratic winds gusting to 70 kilometres an hour spread the flames both to the west and northeast.

At least four roads in the area were closed, and a plume of heavy smoke was visible for kilometres. The cause was unknown.

"It's fast-moving. We've got a lot of wind up there," Boulder County sheriff's Cmdr. Rick Brough said. He said emergency crews were concentrating on evacuations. No injuries were reported.

Homes and cabins are scattered throughout the area, some in old mining communities and others on isolated lots. Authorities said about 100 buildings were threatened, but they didn't know exactly how many structures were destroyed.

Laura McConnell, a spokeswoman for the fire management team, said the homes of four firefighters were among those destroyed.

One fire vehicle was destroyed, said Patrick von Keyserling, a spokesman for the Boulder County Office of Emergency Management.

At least two air tankers were sent to the Rocky Mountain Metropolitan Airport southeast of Boulder to help, but the winds were too strong for them to fly over the fire.

"They just can't get up until the wind dies down," Brough said.

The strong winds accompanied a cold front moving across the state. They weren't expected to slacken until Monday night, said Scott Entrekin, a National Weather Service meteorologist.

Steve Segin of the Rocky Mountain Area Coordinating Center, which manages firefighting equipment and crews, said three hotshot ground crews were dispatched to the blaze.

Three evacuation centres were set up in Boulder and in the mountain village of Nederland, and at least 65 people had checked in at the three centres by mid-afternoon. A shelter for livestock was set up at the Boulder County Fairgrounds in Longmont.