The FBI has raided the offices of the independent government agency established to protect federal whistleblowers. On Tuesday, more than a dozen agents made off with computers and documents belonging to Office of Special Counsel head Scott Bloch. Bloch has been accused of obstructing a 2006 inquiry into his conduct. But critics say the FBI could be trying to intimidate Bloch as he leads probes into the Bush administration. Bloch’s investigations have focused on the firing of US attorneys and the alleged use of federal agencies for political ends.