Four former coal mine officials are scheduled to go on trial Monday in Kentucky for allegedly skirting federal rules meant to reduce deadly dust in underground mines.

The men worked for now-bankrupt Armstrong Coal. Federal prosecutors said they ordered workers at two Kentucky mines to rig dust-monitoring equipment to pass air quality tests.

The defendants in the Kentucky case include Glendal “Buddy” Hardison, a former high-ranking Armstrong official who ran all of the company’s western Kentucky mines. In all, nine Armstrong managers and supervisors were indicted, but five settled their cases before the trial.

The workplace issues came to light when some Armstrong miners contacted a lawyer. One of the men set to testify, Mike Wilson, said he couldn’t see his hand in front of his face down in the mine.

Jury selection is scheduled to began Monday morning in U.S. District Court in Louisville.