The official said the prisoners rushed the facility's main door early today while guards were changing shifts. The official said none of the prisoners who escaped were suspected Islamic militants.
The official insisted on anonymity because he was not authorised to speak to the press.
The official said seven prisoners were back in custody and that officials were searching for the others. Amnesty International has accused Mauritanian security forces of torturing detainees at the prison, located in the Dar Naim suburb of Nouakchott.