OTTUMWA, (AP) - A former child therapist from Iowa serving a five-year sentence on child pornography charges has died as he was being transported between prisons.

Joseph Curtis died on June 23. His death was confirmed on Thursday.

The 66-year-old Curtis worked as a child therapist at Ottumwa Regional Health Center until he was charged in 2007.

The U.S. Marshal's Service says Curtis was being transported from a prison in Leavenworth, Kan., to Terre Haute, Ind., when he stopped breathing.

Authorities say the bus carrying Curtis was less than 3 miles from the Terre Haute prison when other prisoners alerted guards to Curtis.

Curtis was pronounced dead at the prison. Authorties say an autopsy was inconclusive.

Curtis began his sentence in March.