Margot Williams

Known or suspected terrorists who cooperated with federal investigators in at least six major terrorism investigations over two decades were granted protection under the federal witness protection program –- and two of them temporarily could not be found by federal authorities, according to a report from the Justice Department's inspector general.

Five men convicted in a recent wave of high-profile domestic terrorism cases are now in special communications management units (CMUs) in the American Midwest, where their conversations are monitored 24 hours a day by counterterrorism analysts at the U.S Bureau of Prisons in West Virginia.

A new analysis by NPR's Investigations unit shows several new arrivals into the secretive CMU units, based in Terre Haute, Ind. and Marion, Ill.: