Ouray County spokeswoman Marti Whitmore said the miners were underground yesterday at the Revenue-Virginius mine and were confirmed dead yesterday afternoon.
"Anything that has been reported is speculative," Whitmore said. "We don't know what the cause is."
Star Mine Operations, LLC, the owner of the mine, couldn't immediately be reached for comment, but Whitmore said the company has accounted for all workers at the site.
She said 20 people were taken to area hospitals, and all but two have been treated and released. The conditions of the two hospitalised workers haven't been released.
The US Mine Safety and Health Administration is at the accident site.