A detective has been quizzed as part of a probe into gardai suspected of working for the Hutch gang.
The officer, attached to the secretive Special Detective Unit (SDU) which investigates terrorism and organised crime, has been suspended from duty.
The arrested detective was licensed to carry a gun. It's understood cash and ammunition have also been seized.
The Garda National Bureau of Criminal Investigation has been investigating suspected links between members of the gardaí and organised crime.
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The detective garda at the SDU was arrested last Wednesday as part of the probe.
It's suspected he may been involved with the Hutch organised crime group and allegedly dealt with a number of the gang's associates.
Gardaí carried out a number of searches as part of the inquiry, including at the man’s home.
Around €40,000 in cash and a number of rounds of ammunition were seized. The garda was licensed to carry a firearm.
Investigators also removed documents and electronic devices.
Laptops and phones are being forensically examined for emails, texts, and voice messages.
The detective worked in SDU which is responsible for investigating organised and subversive crime including the activities of Irish and international terrorist and organised crime groups.
It is one of the most secretive and sensitive garda departments, with a remit that includes State security.
The officer was detained under section 4 of the Criminal Justice Act at a garda station and released after questioning.
A file is to be sent to the Director of Public Prosecutions.
Garda headquarters confirmed the officer had been suspended.
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