By VICKI SMITHMORGANTOWN, W.Va. (AP) â¿¿ The U.S. Labor Department says it has approved new federal rules that could help save lives at dangerous mines with a pattern of safety violations. The agency says the rules approved Thursday also put more responsibility on companies to find and fix hazards. The changes were first proposed less than a year after the Upper Big Branch mine exploded in April 2010, killing 29 men. It was the worst U.S. coal mine disaster in four decades. Since then, Labor Secretary Hilda Solis says the agency has undertaken "a serious and comprehensive evaluation of mine safety practices." Among other things, the rules let MSHA designate a company a pattern violator without a prior warning.