By Cormac O’Keeffe, Sean O’Riordan and David Raleigh

More gardaí may come under the scrutiny of an internal probe into alleged corruption following the dramatic arrest of three members, including a high-ranking officer.

A superintendent, an inspector and a detective garda were questioned about alleged links to organised crime, specifically a Munster gang.

The allegations include the leaking of information, conspiracy to pervert the course of justice, and drugs offences.

It brings to four the number of gardaí arrested, with the detective garda arrested a second time. His first arrest in January related to a separate suspected offence.

Garda sources said the number of arrests, and the rank of those involved, was “unprecedented”.

“There may have been arrests before of gardaí, but not like this, not three of them, and not a superintendent and an inspector. Usually it’s at garda rank or sergeant,” said a senior source.

It is thought to be the second time a superintendent has been arrested as part of a criminal investigation.

Separate sources said the net may widen to other officers. Commenting on the four arrested so far, one senior source said the number of gardaí under suspicion was “at least that” number.

A separate source said other Garda operations in which these officers were either involved in or had knowledge about could also come under investigation.

A third source said that investigating gardaí had uncovered a “significant problem” and said that he would “not be surprised” if more gardaí came under suspicion.

The source also said that other interactions by these gardaí, beyond the gang under investigation, could well be examined.

The arrests were conducted in the Southern region and relate to an investigation by the Dublin-based National Bureau of Criminal Investigation into alleged links with an organised crime gang in Munster.

This drug gang has connections with a notorious international criminal network based in Munster.

In a statement, Garda HQ provided details of the yesterday morning’s arrest:

The superintendent was arrested for breach of the provisions of section 62 of the Garda Síochána Act 2005 – which relates to disclosing information that is likely to have a harmful effect;

The inspector was arrested under the Misuse of Drugs Act 1977-84, but the specific suspected offence has not been disclosed;

The garda was arrested for suspected conspiracy to pervert the course of justice under common law.

This detective garda was arrested last January on suspicion of leaking information, in relation to CAB operations, to the gang.

This garda was suspended from duty by Garda Commissioner Drew Harris.

Last night, the inspector was released without charge and a file sent to the DPP. He was suspended after his release. The superintendent and garda had the periods of detention extended.

Gardaí spoken to by the Irish Examiner expressed their shock at the arrests.

Last October, it emerged a criminal gang had allegedly blackmailed a serving garda (separate to the other three officers) into providing them with bogus car insurance certificates. The garda in question was arrested.

Some of the leaked information is alleged to be linked to a planned raid last March by the Criminal Assets Bureau (CAB) targeting a suspected money-laundering associate of a Munster gang involved in the drugs trade.

In its biggest seizure of vehicles, CAB took away 115 cars, worth around €2.8m.

It is understood that CAB did not involve local gardaí in that operation because of serious concerns about leaking of information.

The NBCI probe is led by Detective Chief Superintendent Walter O’Sullivan and a team of senior detectives.

It is thought that the investigation involved the interception of communications and surveillance.

Deputy Commissioner Policing and Security John Twomey said: “An Garda Síochána is fully committed to investigating any alleged wrongdoing or corruption involving Garda personnel.”