Computer glitch on Titanic Belfast website
Titanic Belfast has said some "limited personal data" was inadvertently released while people were trying to book tickets for a Game of Thrones exhibition.
Titanic Belfast said online applications were stopped as soon as they it became aware of it.
A full investigation has been launched.
The exhibition is being organised by the Northern Ireland Tourist Board and NI Screen but the event is being held at Titanic Belfast.
In a statement, Titanic Belfast said: "Some limited personal data has inadvertently been released as part of the online booking process for the Game of Thrones exhibition. As soon as Titanic Belfast was aware of this, online applications were stopped, with the fault immediately investigated.
"Titanic Belfast has now instigated a full investigation and has informed the Northern Ireland Information Commissioner's office of this breach. Any customers seeking further clarification can contact Titanic Belfast on 028 9076 6399 or by email: email@example.com
"Titanic Belfast's response to the extraordinary online demand for tickets ensured that a total of 10,500 tickets were secured by Game of Thrones fans, with in excess of 2,000 of these confirmed by our ticket desk via telephone. We are delighted that the exhibition has generated such interest and thank all those fans for their patience."
The Game of Thrones exhibit will run at Titanic Belfast from 8 - 17 June.
Filming for the first three series of Game of Thrones has taken place at various locations across Northern Ireland.