Gardaí in Co Kerry believe four teenagers forged bank notes worth thousands of euro during the Christmas period in the Killorglin area and these were successfully cashed over the following weeks.
It is believed they used a scanner, printer and a computer in one of the teenager's home to forge the notes.
While the bank notes, which had been circulating in Kerry were of poor quality, they were successfully passed in bars and nightclubs late at night.
Gardaí believe there have been at least two, if not three, separate forgery scams operating in the county recently.
They have warned bar and nightclub owners, in particular, to be vigilant as some of the notes are still in circulation.
Up to €5,000, mainly in €50 denominations, was successfully cashed by the four teenage friends, the gardaí believe.
But when one of them tried to pass a forged €50 note in mid January in a shop in Caherciveen, the shopowner alerted the gardaí.
The teenagers have since co-operated with gardaí and identified where the counterfeit money was laundered.
It is understood that some bar and shop owners have been compensated by parents of the teenagers.
The four Killorglin teenagers, although under 18, used the forged money in nightclubs and bars where its poor quality would not have been easily spotted by busy staff in sometimes poorly lit areas.
Notes were passed in bars and nightclub counters in Dingle, Kenmare and Killarney.
A file is being sent to the DPP on the matter but because the four are minors, they may be dealt with under the juvenile liaison scheme, according to an investigating garda.
A separate operation has been operating in Tralee. Again, larger denominations were involved.
The possible use of the Internet in one of the forgery operations, with individuals downloading images from the official European Commission website on the euro, is being investigated.
According to the Garda Press Office, this was tried in the early days of the euro in Co Kildare, but resulted in crude notes which were easily spotted, with the front and back having to be pasted together.
Mr Peter Doyle, director of the European Commission Representation in Ireland, said there had been attempts to counterfeit the euro in different parts of the EU but none had succeeded.
Texture as well as state-of-the-art markings had been impossible to imitate in the new currency.
It would be impossible to successfully forge a note from the commission's website, he said.