A Revenue Commissioners official in his 50s who was questioned by gardaí in Dublin on suspicion of involvement in tax evasion was released without charge last night.
A file is being prepared for the DPP.
His arrest and questioning at Blanchardstown Garda station followed 30 raids on homes and businesses carried out by gardaí and Customs officers around Dublin city yesterday morning.
Overseen by the Criminal Assets Bureau (Cab), "Operation Tie", which started at 6am and lasted three hours, saw officers seize 40 luxury cars and a handgun, and large quantities of legal and financial documentation.
More than 60 gardaí were involved in yesterday's operation, which also involved members of the Organised Crime Unit, the National Bureau of Criminal Investigation and Revenue investigators.
Officials are looking at whether people were importing new and used cars into the country and then paying vehicle registration tax (VRT) at the basic rate, despite the vehicles being high specification models, which should have attracted the top rate of VRT.
The loss of revenue to the exchequer was as high as €20,000 per vehicle in some cases.
Others have recently invested money in property through a solicitor who is believed to have lost some of the funds due to the softening housing market in the Republic and abroad. This element is being separately investigated by the Cab.