Sex offenders who failed to register nabbed

(CNN) -- Authorities concluded a three-year operation that resulted in the arrests of 345 sex offenders who failed to register with state authorities, the U.S. Marshals Service said on Tuesday.

"Operation Guardian" targeted 444 of the nation's most dangerous sex offenders who had violated regulations for keeping track of their whereabouts.

In addition to the arrests, the Marshals Service said 82 people who live outside the United States were located but no immediate information was provided about their status.

Law enforcement continues to seek the remaining 17 people on the list.