Preliminary information from the U.S. Mine Safety and Health Administration’s (MSHA) investigation of two fatalities at a Colorado silver mine on Nov. 17 indicate that the miners died of carbon monoxide poisoning after entering an area of the mine where an explosive had been previously detonated, federal investigators said.

Nick Cappanno, 34, of Montrose and Rick Williams, 59, of Durango were killed at the start of their shift Nov. 17 at the Revenue-Virginius mine near Ouray in southwestern Colorado.

According to reports, Cappanno entered the area first and when he did not return Williams, a mine foreman, followed him into the area. The men were found by other miners who immediately evacuated the underground gold, silver and lead mine, said Amy Louviere, a spokeswoman for MSHA, which is investigating the deaths.

Mine manager Rory Williams previously said there was a blast in the mine to remove rock on Nov. 16 that may have been a source of the carbon monoxide. Louviere said the blast occurred during the previous shift, so the accident could have happened on Nov. 16, the Associated Press reported.

Nineteen miners were taken to a hospital for treatment and all have been released.

About 100 miners work at the site, about 270 miles southwest of Denver, which will be closed until the end of the investigation.
Regulators weren’t aware of any previous carbon monoxide problems.

The mine dates to the 1870s and was taken over by its current owner, Denver-based Star Mine Operations, in 2011. The company, which also has a mine in Cerro Blanco, Peru, received a permit to resume mining at the site near Ouray in February 2013. All the mining is done by drilling and blasting, according to state regulators.

Federal records show the mine reported eight employee accidents in the past two years, including five that resulted in days away from work for the injured worker, the Associated Press reported.

The mine has received 33 citations since Star Mine became the operator, including 13 that regulators determined were reasonably likely to result in injury or illness. The most recent came last month after inspectors found tire chains stacked in a walking area that created a tripping hazard.