A Ministry of Justice spokesman said: "We treat the security of information very seriously and took immediate steps to recover the data as soon as the loss was reported to ensure that it went no further.
"These types of incidents are extremely rare but this does not mean that we are complacent.
"A thorough investigation was held by the prison who immediately altered their procedures, and further changes were implemented across the prison estate."
More top news
Northern Ireland's abortion laws break the EU human rights convention, Belfast High Court has ruled.
Amid calls for new laws to prevent models getting too thin, ITV News speaks to three women in the fashion industry to get their views.
Police reopen investigation into brutal murder of David Clarke, 14-years after he was "savagely beaten" to death in his own home.