RENO (AP) — Three Congress members upset about the lack of prosecution of federal gun cases in Northern Nevada are stepping up pressure on U.S. Attorney General Eric Holder to explain why U.S. prosecutors appear to be feuding with the Bureau of Alcohol, Tobacco, Firearms and Explosives.Iowa Sen. Chuck Grassley, ranking Republican on the Senate Judiciary Committee, has been pressing the U.S. Attorney’s Office in Reno for information since the Reno Gazette-Journal first reported the rift last month.Nevada Republicans Sen. Dean Heller and Rep. Mark Amodei joined Grassley in another letter Monday. They want to know why assistant U.S. attorneys in Reno refused to pursue eight cases ATF recommended for prosecution.Heller says the dispute that apparently resulted in most of Reno’s ATF agents transferring elsewhere is threatening Nevada’s public safety.