The Mine Safety and Health Administration says it’s uncovered troubling safety violations in surprise inspections at four underground mines. MSHA says it found “numerous” violations including failure to follow ventilation plans, inadequate roofing, and accumulation of explosive materials. The mines are located in Kentucky, Tennessee and West Virginia. The probes come as MSHA continues to investigate the April 5th deaths of twenty-nine miners at Massey Energy’s Upper Big Branch mine in West Virginia.