Two men have already been convicted of abusing teenagers at the Medomsley Detention Centre, which has now been demolished.
Former prison officer Neville Husband was jailed in 2003 for abusing boys in his care. A store man at the borstal was also jailed.
But police suspect other people may have been involved and that there might be many more victims. They are appealing for anyone with new information to come forward.
Source ITV News