Conditions in the Lucky Friday Mine’s main shaft have parallels to problems at a Nevada gold mine where a 2010 shaft accident claimed the lives of two workers, a top official at the federal Mine Safety and Health Administration said Thursday. During recent visits to the underground silver mine in Mullan, Idaho, federal inspectors became concerned about workers’ safety “because of conditions in that shaft,” said Joseph Main, assistant secretary of labor for mine safety and health, in a phone interview from Washington, D.C.