In 18 months of searching, Justice Department Inspector General Glenn A. Fine and Office of Professional Responsibility chief H. Marshall Jarrett have uncovered new e-mail messages hinting at heightened involvement of White House lawyers and political aides in the firings of nine federal prosecutors two years ago. But they could not probe much deeper because key officials declined to be interviewed and a critical timeline drafted by the White House was so heavily redacted that it was virtually worthless as an investigative tool," the authorities said. "We were unable to fully develop the facts regarding the removal of [David C.] Iglesias and several other U.S. Attorneys because of the refusal by certain key witnesses to be interviewed by us, as well as the White House's decision not to provide ... internal documents to us," the investigators concluded in their report. Attorney General Michael B. Mukasey on Monday named a veteran public-corruption prosecutor, Nora R. Dannehy, to continue the investigation. Investigators urged Dannehy to focus on the dismissal of Iglesias in New Mexico. He was the subject of repeated complaints by Republican lawmakers to White House and Justice Department officials in 2005 and 2006 over not bringing voter-fraud and corruption charges against Democrats. Their report said the internal probe at Justice could not reach Miers and Rove, "both of whom appear to have significant first-hand knowledge regarding Iglesias's dismissal."