RAPID CITY, S.D. (AP) - In a six-count indictment, a federal prison inmate is accused of mailing threatening letters to his former attorney, a federal probation officer and to their spouses.

Thirty-three-year-old Thomas Jensen of Englewood, Colo., has pleaded not guilty in Rapid City federal court.

Documents allege Jensen wrote letters last year threatening to hurt each of the four recipients, all of whom live in Rapid City.

In 2004, Jensen was sentenced to 33 months in prison for assaulting a federal officer and to another 18 months in 2007 after a judge said he violated his conditions of release by stalking, failing to attend mental health counseling and threatening a U.S. probation officer.