WESTCLIFFE, Colo. (AP) — Authorities say a Kansas teenager who died at a Colorado church camp likely had a blood clot that lodged in his lung.

Custer County Sheriff Shannon Byerly said in a news release that preliminary autopsy results indicate that 16-year-old Demarius Cox, of Hillsboro, Kansas, had a pulmonary embolism. Emergency crews rushed to the Sky Ranch Horn Creek summer camp Friday morning after receiving a report that the teen wasn’t breathing. The camp is in a rural area of the Rocky Mountains near Westcliffe, about 150 miles (241 kilometers) southwest of Denver.

Demarius had been visiting the camp as part of a Hillsboro church’s youth group. He had run track this year for his high school.