Up to €50m worth of cigarettes have been seized in Greenore port in Co Louth from a cargo ship that originated in the Philippines.
Nine men, including two of the ship's crew, have been arrested for questioning. The suspects include seven Irish men aged between 19 and mid 40s, one Lithuanian in his 50s and one Ukrainian in his 40s.
They are being detained in various garda stations in Co Louth and Co Monaghan.
Revenue officials seized cargo from the vessel MV Anne Scan during an operation known as 'Samhna'.
The Naval Service kept the vessel under surveillance, as they suspected that a large consignment of contraband cigarettes was concealed within the cargo.
The ship arrived yesterday morning with a cargo said to be animal feed.
When the cargo was discharged, gardaí and customs officials seized the cigarettes and searched the ship.
Revenue officials believe the haul contains more than 120m cigarettes with a retail value of about €50m.
Garda Commissioner, Fachtna Murphy said: 'This is a significant strike against organised crime. The success of the operation illustrates the results and benefits that flow from close interagency cooperation.'
More 150 officers from agencies on both sides of the border participated in the operation.
Using AIS (Automatic Identification System), the operation centre was able to track the vessel from the Mediterranean to the Irish Sea.
Once the vessel was in the Irish Sea, the LE Niamh tracked it using onboard sensors while at the same time keeping out of visual range.