Authorities say five hikers have been trapped by a rock slide on a popular trail near Agnes Vaille Falls in Chaffee County.
One hiker has been pulled out and flown to a hospital.
The Chaffee County Sheriff's Department says the slide occurred about 11 a.m. Monday in the Pike and San Isabel National Forest about six miles west of Nathrop in Chalk Creek Canyon, which is beneath Mount Princeton and on a road that leads to the mining town of St. Elmo.
Authorities say a teenage girl was extracted from the slide and flown to a hospital. The nature and extent of her injuries weren't available.
Officials say a seventh person is unaccounted for.
The names, ages and hometowns of the victims haven't been released.
Chaffee County spokesman Dave Cotten said there were "serious injuries" during the slide.
Cotten said Salida Fire Department and State Patrol crews were helping Chaffee County emergency agencies in the search. There were no reports as to how far up the trail the rock slide occurred.
Three air-ambulance helicopters responded to the incident, according to The Mountain Mail newspaper.
The Colorado Department of Corrections said that the Buena Vista K-9 unit was sent to help the sheriff's office with search and rescue, according to The Denver Post.
County Road 162 is closed to all non-emergency traffic beyond County Road 270.