Federal prosecutors have subpoenaed more than a dozen staffers working for retiring state Sen. Robert Mellow as part of an ongoing probe into public corruption in Northeast Pennsylvania, sources said Monday. About 15 staffers at the Democratic leader's offices in Peckville and Harrisburg received the hand-delivered subpoenas beginning last week from the FBI, ordering them to appear before a grand jury sitting in Harrisburg on Aug. 19, sources said. The subpoenas are the latest development in the federal investigation of Mr. Mellow, whose Peckville office and home were searched by teams of FBI and IRS agents on June 18. The...