Patriot Coal Corp. has resumed production at its Federal No. 2 mine near Fairview.
St. Louis-based Patriot said late Wednesday its improved ventilation plan was approved by federal regulators.
The mine shut down Feb. 18 after dangerous atmospheric conditions were detected in a sealed area.
Federal mine safety rules require action if methane levels in sealed areas reach explosive ranges.
The Mine Safety and Health Administration adopted the rule after a January 2006 explosion at the Sago Mine trapped and ultimately killed 12 men.
Chief Executive Richard Whiting says maintaining a safe environment will be Patriot's highest priority.
MSHA is currently investigating the alleged falsification of safety inspection reports at the Federal mine.
