Company president Jim Cooper said plans included sealing off about two-thirds of the operation to arrest further air contamination by forcing a cut-off to the air supply, the Grand Junction Daily Sentinelreported.

While Cooper did not respond to an ILN request for comment, the paper reported that some of the 340 workers left in limbo by the gas issue were returning to their jobs.

No timeframe for completing the ventilation plan was indicated.

Also last week, a section of Elk Creek was under a federal order halting production after a bounce that geological experts tied to a 2.8 magnitude earthquake in the area on January 3.

US Mine Safety and Health Administration spokeswoman Amy Louviere said the mine near Paonia had suffered the second of two bounce events, though the specific time of the incident could not be confirmed.

An initial bounce occurred at the operation on December 2.

It was not clear Wednesday if that portion of the mine had been cleared of the federal K order.

The Paonia area is home to three underground coal mines, including Oxbow as well as Bowie and West Elk.

Bounces and burst are more common in the western US coalfields, which often have more overburden than their Appalachian counterparts.

In all, there are a dozen coal operations in the state, including nine underground mines in Delta, Garfield, Gunnison, La Plata, Las Animas, Rio Blanco and Routt counties and three surface mines in Moffat and Montrose counties.