Seven guards at a prison operated by the District of Columbia have been charged with distributing crack, powdered cocaine or marijuana to inmates. The officers were named in six indictments unsealed in U.S. District Court in Alexandria, Va. Their arrests were the result of a six-month undercover FBI investigation in which an inmate was an informant, officials said. Federal prosecutors said Friday that the probe revealed how guards at the Lorton Correctional Complex in Fairfax County, Va., enlisted inmates to make drug sales and arranged payments from outside the facility. They also alleged that the guards took bribes. U.S. Attorney Henry E. Hudson added, however, that the officers were not believed to be involved in a coordinated drug trafficking effort. ``What we have here are a number of isolated instances, all occurring at about the same time,'' he said during a Friday news conference. The investigation uncovered no widespread drug abuse by Lorton officers, said Walter B. Ridley, director of the District of Columbia Department of Corrections. His department runs the complex. The FBI launched the investigation because Lorton inmates appeared to have continual access to illegal drugs, said Thomas E. Duhadway, director of the FBI field office in Washington. Officials said charges against the officers ranged from possession with intent to distribute to introduction of narcotics into a prison. Each faces at least three counts. A civilian also was charged with possession of marijuana and cocaine. All those charged were released on personal recognizance bonds and ordered to appear for arraignments Monday in the Alexandria court.