Clever detector dog Waffle sniffed out nearly 600,000 cigarettes hidden in a container at Dublin Port.
Revenue officials seized 594,000 cigarettes branded "Minsk" bearing a Russian stamp that had arrived from Belgium.
They have an estimated retail value of €445,500, representing a potential loss to the Exchequer of €350,100.
Last week officials found 180,000 cigarettes with an estimated retail value of €135,000 at Dublin Port.
They represented a potential loss to the Exchequer of €106,000.
The illegal cigarettes branded ‘Minsk' and ‘NZ Gold’ were discovered, with the assistance of Revenue’s detector dog Kelly, in a container that had arrived from Lithuania.
A spokeswoman for Revenue said: "Investigations into both seizures are ongoing.
"These seizures are part of Revenue’s ongoing operations targeting the supply of illegal tobacco products. If businesses or members of the public have any information regarding smuggling they can contact Revenue in confidence on the confidential free phone number 1800 295 295."
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