Fifteen gardaí in the south of the country have been questioned as part of a criminal investigation into suspected road traffic offences which were not prosecuted.

Officers from the National Bureau of Criminal Investigation carried out a number of searches, including at a garda station, during the week and seized documents, paper and computer records.

Phones were also seized from gardaí and GAA players and officials.

The searches and seizures represent an expansion of an ongoing criminal investigation into garda corruption which began after it was suspected that confidential information about garda operations was being leaked to an organised crime gang in the south of the country.

The investigation is being led by the NBCI and this aspect is focused on road traffic offences and why certain offences, including penalty points offences, were not prosecuted.

The investigation is examining both recent and historic cases which occurred before the introduction of the new centralised system for the cancellation of penalty points.

The people not prosecuted for road traffic offences include GAA players and officials.

The NBCI officers carried out a number of searches and seized phones from gardaí and GAA members as well as documents, files, summonses, computer and paper records relating to the offences.

They are also examining if offences against criminals were not proceeded with in return for information on more serious crime.

Detectives have questioned, but not under caution, at least 15 gardaí about summonses they may not have proceeded with.

All are believed to be co-operating with the investigation, which is also examining if any of them may have been put under any pressure by more senior officers not to proceed with prosecutions.

The searches and interviews were carried out over a number of days this week.

The investigation is continuing.