The Clear Creek County Sheriff's Office said the snow slide occurred between 1 p.m. and 2 p.m. at Loveland Pass outside the boundaries of the Loveland Ski Area, The Denver Post reported.
"I believe that at this point in time everyone is accounted for, but I'm not sure," Sheriff Don Krueger said.
The snowboarder who survived was able to walk around.
The names of the victims were not available.
Colorado Transportation Department officials reported online about 3:30 p.m. a snow slide had closed U.S. 6 at Loveland Pass, the Post said.