A financial transaction involving a food exporting firm is being investigated by detectives who arrested and questioned a prominent former politician earlier this week.
The transaction is believed to involve a substantial sum of money which gardai suspect may have been the proceeds of drug-trafficking.
The former politician was released late on Wednesday night after being questioned for 36 hours at Pearse Street Garda station in Dublin about suspected money-laundering offences. A file on his case is to be sent to the Director of Public Prosecutions.
Yesterday a second man was arrested at Dublin Airport and taken to Pearse Street Garda station, where he was held under the Criminal Justice (Drug Trafficking) Act 1996, which allows detention for up to seven days.
He has been linked to a drug dealer nicknamed The Penguin, who has made his fortune from selling cannabis in west Dublin. The dealer is currently abroad and believed to be living in Amsterdam.
The Penguin is one of a number of drug-traffickers in Dublin who have been targeted by the Criminal Assets Bureau, which tracks criminals' wealth and has the power to seize assets suspected of being the proceeds of crime.
Gardai believe criminals have made renewed efforts over the past year to "legitimise" their wealth by establishing companies through which drug money can be processed and "cleaned". The legislation enacted last year in the wake of the murder of the journalist Veronica Guerin is believed to have led to a flurry of activity as criminals sought to find new ways to channel their wealth into legitimate activities.
The bureau is also investigating the use of professional advisers by such criminals.