Authorities say two people are dead after a Black Hawk helicopter from Kentucky's Fort Campbell crashed into the side of the Colorado's second-highest mountain.
Lake County Sheriff spokesman Max Duarte says one person was flown to a Denver hospital after Wednesday's crash and rescue teams were searching for the fourth person aboard.
Duarte says he doesn't have information about the identities of the dead and injured.
He says the Kentucky-based chopper was training in central Colorado when it struck the 4,328-metre tall Mount Massive.
The US Forest Service says its workers building trails with a youth group heard the crash but didn't see it.