CIA Director Michael Hayden has mounted a highly unusual challenge to his agency's chief watchdog, ordering an internal investigation of an inspector general who has issued a series of reports sharply critical of top CIA officials. Hayden is seeking to rein in an inspector general who has used the office to bring ... scrutiny upon CIA figures from former Director George Tenet to undercover operatives running secret overseas prison sites. The investigation is focused on ... CIA Inspector General John Helgerson and his office, particularly whether they were fair and impartial in their scrutiny of the agency's terrorist detention and interrogation programs. Officials said that the investigation also will span other subjects and that it already has expanded since its start months ago. U.S. intelligence officials concerned about the inquiry said it is unprecedented and could threaten the independence of the inspector general position. The investigation could at least lead to appearances he's trying to interfere with the IG, or intimidate the IG, or get the IG to back off," one U.S. official familiar with the investigation said. Frederick Hitz, who served as the CIA's inspector general from 1990 to 1998, said the move will be perceived as an attempt by Hayden "to call off the dogs." "What it would lead to is an undercutting of the inspector general's authority and his ability to investigate allegations of wrongdoing," Hitz said. "The rank and file will become aware of it, and it will undercut the inspector general's ability to get the truth from them." Hayden has been a staunch defender of the Bush administration's counterterrorism programs.