A wildfire near the University of Colorado in Boulder that may be man-made burned about 62 acres (25 hectares) of woodland on Sunday and prompted the evacuation of 426 homes in the drought-hit region, authorities said.
The fire in Sunshine Canyon, just outside the university town, started before dawn on Sunday, with no injuries or damage to structures reported, said Commander Mike Wagner, a spokesman for the Boulder County Sheriff's Office. The Boulder Office of Emergency Management said the blaze was 50 percent contained.
Authorities ordered the evacuation of 426 homes, with about 800 others on notice to be evacuated if winds shift, Wagner told reporters. Evacuation orders will remain in place overnight.
Authorities have ruled out a lightning strike or other natural cause for the fire. The area is crossed by hiking trails and is home to transient camps, Wagner said.
"That causes us to speculate it's human-caused," he said.
A wide swath of northeastern and north-central Colorado was under a National Weather Service "red flag" warning for wildfires because of winds gusting to 40 mph (64 kph) and near-record-high temperatures.
Much of Colorado, Kansas, Oklahoma, New Mexico and Nebraska are in drought conditions ranging from moderate to extreme, the agency said.
Prairie fires stoked by high winds and tinder-dry vegetation raged across 1.5 million acres (600,000 hectares) of the southern Great Plains early this month, killing at least six people and prompting thousands of people to be evacuated.
(Reporting by Ian Simpson in Washington; Additional reporting by Keith Coffman in Denver; Editing by Sandra Maler and Peter Cooney)