Patriot Coal has fired one employee and put two others on administrative leave while federal regulators investigate claims of falsified inspection reports at the Federal No. 2 mine near Fairview.
St. Louis-based Patriot reported the disciplinary action last week in a filing with the Securities and Exchange Commission but didn't identify the workers.
Spokeswoman Janine Orf declined comment Thursday but said Patriot takes safety seriously.
The filing says an internal investigation is under way, and Patriot is cooperating in the federal probe.
A Patriot foreman, 40-year-old John Renner of Granville, has been charged with falsifying methane-test records but is cooperating with prosecutors.
His attorney did not immediately respond to questions Thursday.