Convicted drug smuggler John Gilligan has been taken to hospital in Dublin for tests after complaining of pains in his chest and arm earlier this week.
Mr Gilligan has been receiving treatment at Portlaoise Prison for a number of days, but was moved to Dublin under heavy escort this afternoon.
The Irish Prison Service has not revealed the reason for the move, but it is believed to be related to a heart condition.
Mr Gilligan is currently serving 28 years in prison for importing cannabis.