A retired senior garda officer is still being questioned as part of an investigation into the activities of an organised crime gang in Dublin.

The 61-year-old was arrested last Wednesday on suspicion of enhancing the ability of a criminal organisation to commit or facilitate a serious offence.

Over thirty kilos of cannabis with an estimated street value of €600,000 and €47,000 in cash have been seized.

A serving garda based in a Dublin garda station has also been suspended from duty in connection with the investigation.

The Garda Commissioner suspended the man, who works as a detective, last Friday morning.

The inquiry is being led by the Garda National Bureau of Criminal Investigation, which is also investigating if confidential information relating to organised crime operations was disclosed to members or associates of the criminal gang.

Gardaí say the investigation is ongoing.

The 61-year-old retired officer is being detained under anti-gang legislation and has had his period of detention extended three times, twice by senior garda officers for the first 48 hours and once by a District Court judge for a further 72 hours.

He can be detained at Irishtown Garda Station until tomorrow, by which time he must be charged, released, or have his detention period extended for a further final two days by a District Court judge.

Gardaí also said that three other gardaí have been suspended in connection with separate investigations by a divisional and specialist unit.

A male garda serving in Dublin was suspended last Tuesday in connection with an inquiry being conducted by the Anti-Corruption Unit.

Two other gardaí in south Dublin were arrested and questioned following a complaint by a juvenile alleging an incident at a south Dublin garda station earlier this year.

Garda Headquarters also says these investigations are ongoing.