The Garda Ombudsman Commission asked the Garda Commissioner to investigate the attendance by one of its experienced investigators at the party last Monday week
A man has been arrested as part of the investigation into a GSOC investigator attending a party alongside Gerry 'The Monk' Hutch.
The man - who is in his 60s - is being detained at a Garda Station in the east of the country.
The party was held in Dublin the night Mr. Hutch was acquitted of the murder of David Byrne last week.
A home in the Dublin 3 area has also been searched by gardaí.
GSOC asked the Garda Commissioner to investigate the attendance by one of its experienced investigators at the party last Monday week.
The party was organised to celebrate Mr Hutch’s acquittal and release from custody after 20 months in prison on remand.
Detectives from the NBCI commenced their investigation last Monday morning.
They interviewed the former GSOC investigator, who confirmed he attended the party.
The man served as a police officer in another country outside Europe before joining the Garda Ombudsman and coming to Dublin.

Liam And Lily Were The Most Popular Baby Names In Kildare Last Year
Reminder To Landowners: Hedge-Cutting Season Is Ending This Weekend
Man Charged With The Murder Of English Tourist Following Temple Bar Incident Last Year
Two Health Insurance Companies To Increase Their Prices From April, With Families Facing A Likely €180-€330 Increase
Nearly 320,000 People Behind On Electricity Bills In 2025
Kildare Ministers Martin Heydon And James Lawless Declare Rental Income In 2025
IFA Plan Large Protest This Saturday In Newbridge
Gardaí Say 'Current' Phase Of Searches Linked To Missing Deirdre Jacob And Jo Jo Dullard Have Ended