A man in his 40s has been arrested.
Revenue has seized more than 3.3 million cigarettes at Rosslare Europort in Co. Wexford.
Officers stopped a Polish registered truck which came on a ferry from France and found the cigarettes within its load.
They have a retail value of 2.4 million euro, which is a potential loss to the exchequer of over 1.8 million.
A man in his 40s is being questioned as part of the investigation.