A Garda inspector who was among three members of the force arrested on suspicion of corruption earlier today has been released without charge.
He was suspended from duty immediately upon his release and investigators said a file will now be prepared for the DPP.
A Garda superintendent and a member of Garda rank remain in custody and have had their periods of detention further extended.
In a statement earlier, the force said this morning's arrests came during an operation led by the Assistant Commissioner for Special Crime Operations.
Several premises in the southern part of the country were also searched this morning as part of the operation, which is linked to an investigation into a Limerick criminal gang.
Investigators said the three members can be held for up to 24 hours.
There have been two previous arrests of gardaí as part of this investigation.
It is suspected information has been disclosed to the criminal gang about a CAB investigation into its activities.
The superintendent was arrested for suspected breach of the provisions of section 62 of the Garda Síochána Act, 2005.
The act requires members of the force to not disclose any information obtained in the course of carrying out duties "if the person knows the disclosure of that information is likely to have a harmful effect".
The Garda Inspector was arrested for suspected breach of provisions of the Misuse of Drugs Act, 1977-84.
Finally, the member of Garda rank was arrested for suspected conspiracy to pervert the course of justice.
Deputy Commission John Twomey said the three members were arrested for questioning on suspicion that they have "been involved in the commission of one or more criminal offences."
He explained: "An Garda Síochána is fully committed to investigating any alleged wrong-doing or corruption involving Garda personnel, and will work with other relevant agencies in doing so.
"As this is a live and ongoing investigation, it is not appropriate to make any further comment at this time”.
Justice Minister Charlie Flanagan said he can't comment on individual cases, but expects "a thorough and timely investigation".