The National Weather Service said the twister was confirmed by radar at 2:20 p.m. MDT. The weather service said a tornado warning was issued for northeastern Denver County and western Adams County, but expired at 2:45 p.m., The Denver Post reported.
The newspaper said people sought shelter in restrooms, stairwells and other interior areas until the all-clear call was given, airport spokesman Heath Montgomery said.
Montgomery said no planes took off or landed during the warning period. He said he didn't know if any planes were diverted.
He said there were no reports of damage or injuries.
Frontier Airlines spokeswoman Kate O'Malley said the airline's passengers who were already on aircraft were hustled back into the terminal.