The lightning hit around 11:30 a.m. on the popular 14,000-foot-plus mountain about 40 miles west of Denver.
Search and rescue teams and an Army National Guard high-elevation helicopter responded to the strike and all the hikers were able to get off the mountain.
The Clear Creek Sheriff's Office says eight adults were transported by emergency medical personnel from the trailhead. Five refused further treatment but the other three were taken to Denver area hospitals, including one person in serious condition.
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