By Keith Coffman
DENVER (Reuters) - Carbon monoxide poisoning was responsible for killing two miners and sickening 19 others at a gold and silver mine in southwestern Colorado over the weekend, state and federal authorities said on Monday.
The U.S. Mine Safety and Health Administration, which is conducting the probe, said in a statement that a foreman and a miner were "overcome by gases following an explosives accident."
The agency said investigators were still trying to determine what caused the accident at the Revenue-Virginius mine in Ouray County on Sunday and why the miners were unable to escape the fumes.
The facility, located about 330 miles southwest of Denver, is owned by Star Mine Operations, LLC of Denver.
The Colorado Division of Reclamation Mining and Safety, which regulates environmental impacts at state mines, said in a statement that Star Mine obtained a permit to mine silver, gold and sulfide materials in February.
"All mining at the site is conducted underground via drill and blast methods," the statement said.
The facility was last inspected in September to certify that an underground ore-processing mill complied with state regulations, the agency said.
The dead men were identified as Nick Cappanno, 34, and Rick Williams, 59. Both were Colorado residents.
An emergency 911 call was placed early Sunday morning to report that some type of mishap had occurred at the mine, said Ouray County spokeswoman Marti Whitmore.
Rescue workers retrieved the bodies of the two victims from an underground shaft, and the Ouray County coroner concluded the men died of carbon monoxide toxicity, she said.
Nineteen workers were treated at area hospitals and all are expected to recover, according to Whitmore. Authorities initially said that 20 workers had been hospitalized.
The Revenue-Virginius mine was first claimed in the 19th century, and is located at an elevation of 12,000 feet along the so-called Governor Basin in the rugged San Juan Mountains.
(Editing by Dan Whitcomb and Marguerita Choy)