A large-scale illegal vodka distilling and bottling plant was discovered when customs officers raided a house and a farm in the Castletowncooley area of the Cooley Peninsula in Co Louth over the weekend.
Among the items seized were thousands of counterfeit labels for well-known brands of the spirit including Smirnoff and Glen; the latter is only sold in Scotland.
Three people including a man in his 50s and one in his 20s were found at the two locations and questioned by officers.
Customs sources said the illicit alcohol would have been sold to unsuspecting members of the public during the festive period.
A senior customs source has advised the public not to buy spirits at open air markets as the majority of it is illegally produced, often in unhygienic conditions such as farm sheds and outhouses.
The source specifically mentioned markets such as that held in Jonesboro, south Armagh. Branded bottles of spirits with what appear to be genuine labels have been bought there but later found to be counterfeit.
This was the latest in a series of raids by customs officers and followed a lengthy surveillance operation based on intelligence gathered by customs investigators.
As well as 1500 litres of pure alcohol, which on its own would have amounted to €74,000 in lost revenue to the Exchequer, the plant had the capacity to produce and distribute enough spirits to cause the loss in excise and other duties of €3 million in one year.
Printing presses for the counterfeit labels as well as a capping machine for counterfeit foil tops were also seized.