Two miners are dead, and emergency workers are trying to reach two others trapped at the Revenue-Virginius mine in Ouray, according to Ouray County spokeswoman Marti Whitmore.
Twenty people, one of them in critical condition, were taken to hospitals in the area after an accident at the mine, which is six miles south of Ouray, was reported to the sheriff's office after 7:20 a.m.
Whitmore said she didn't know what had happened at the mine, but the Ouray Watch newspaper reported there was an explosion.
The Star Mining Company in Denver, owner of the mine, couldn't be reached for comment.
The Watch reported that "mine manager Rory Williams of the Star Mining Company said the injuries were a result of miners breathing in gases and chemicals in the air following a blast."
The two miners who remain underground are in an area that is accessible, Whitmore said, and the sheriff's department, Ouray Fire Department, Ouray County Emergency Medical Services and others are working to reach them.
"We don't know if they are alive. We know that it is not like there was a cave-in and they are behind rocks," Whitmore said.
Star Mining has accounted for all personnel who were at the site and is contacting the federal Mine Safety and Health Administration, according to the county.
At least 14 were affected by gases in the explosion, nitrogen dioxide and carbon dioxide, according to the Watch.