Investigators have confirmed that lightning started a 350-acre wildfire burning near the Colorado-Wyoming border.
The Starwood Fire broke out Sunday afternoon after storms moved through the area west of U.S. Highway 287. It grew quickly in dry, windy weather but was 35 percent contained Tuesday.
About 30 structures are threatened by the fire but no damage or injuries have been reported.
The fire area is part of a large swath of Northern Colorado classified by the U.S. Drought Monitor as "abnormally dry," the precursor to drought.