Gardaí from the Criminal Assets Bureau along with customs officers have seized cars, documentation and a handgun after a series of 30 raids on homes and businesses in Dublin today.
It is understood the raids related to an ongoing investigation into tax irregularities in the motor trade.
A man in his 50s, believed to be an employee of the Revenue Commissioners, was arrested. The raids were the culmination of a nine-month operation dubbed Operation TIE, a Garda statement said.
Gardaí were investigating criminal activity, primarily revenue irregularities and profits deriving from criminal activity, the statement added.
"Between 6am and 9am this morning officers engaged in Operation TIE searched a total of 30 premises which included private houses; business premises and professional offices. A quantity of documentation was seized during the course of these searches, along with a number of vehicles and a 9mm handgun."
While searches took place throughout the city, the bulk were concentrated on locations in the Dublin 12 / Naas Road area, according to the Garda.
"One man in his 50s was arrested...and is currently detained at Blanchardstown Garda station under the provisions of section 4 Criminal Justice Act."
The operation is "ongoing", the Garda statement concluded.
Separately, two people have been released from Garda custody in Dublin after they were questioned about the seizure of a firearm and ammunition.
The man and woman were arrested in the St Anne's Park area of Raheny as a result of an ongoing operating targeting the sale and supply of drugs, a Garda statement said.
The operation was carried out over a period of time by Raheny gardaí as part of Operation Anvil.
A 45-year-old man and a 31-year-old woman were stopped leaving St Anne's Park last Monday evening and a handgun and ammunition were seized. Both were arrested and taken to Raheny and Clontarf Garda Stations.
They were both released from custody last night and a file will be sent to the Director of Public Prosecutions.