The official statement reads as follows:
"It is with great regret that Aiken Promotions today announce that the five concert Garth Brooks Comeback Special Event at Croke Park has been cancelled. No concerts will take place. The ticket return process will be outlined tomorrow. Aiken Promotions have exhausted all avenues regarding the staging of this event. We are very disappointed for the 400,000 fans who purchased tickets for The Garth Brooks Comeback Special Event."

There's also been a statement issued by Ticketmaster Ireland.
"We are working on a plan to make the cancellation process as simple and convenient as possible for customers," they say. "However the scale of this operation is unprecedented in the Irish entertainment industry and therefore we would ask customers to continue to be patient while we finalise our plan. Full details of the plan will be published tomorrow."