Investigators released the names of two men who were killed by an avalanche while they were snowmobiling northwest of Rocky Mountain National Park.
Twenty-five-year old Jacob Kroeger of Stockton, Iowa and 32-year-old Gabriel Medina of Wilton, Iowa died on New Year's Day .
Larimer County sheriff's spokeswoman Eloise Campanella says the coroner ruled the men suffocated.
Witnesses say the two men were competing to see who could drive their snowmobile farthest up a hillside.
Experts say the practice, also known as "high-marking," can cause a snowslide.
Five other people were able to escape the avalanche that suffocated the two snowmobilers.