Now 11 Portlaoise prison inmates treated for suspected overdoses ...

Three of these prisoners are in a critical condition in the Intensive Care Unit of hospital while the other eight remain in a serious condition.

One of the men is “clinging to life” in a critical condition in hospital while the condition of some of the other inmates is described as “serious”.

A number of prisoners were taken to Midlands Regional Hospital Portlaoise by ambulance this afternoon while others received treatment at the prison.

As of Tuesday night, one of the prisoners was in a coronary care unit, eight were in A&E and another was in a secure room in hospital.

A spokesman said: “The is a live operational situation for the IPS and the HSE. Both agencies are working to provide the highest quality health service to those impacted.

“A number of people are currently receiving medical treatment both in prison and in hospital.”

The suspected overdoses happened on the C wing of the prison, which houses a number of convicted killers and gangland criminals.

One of the prisoners hospitalised after overdosing is a gangland criminal in his 40s who is serving a life sentence for murder.

From Dublin’s south inner city, he was convicted for his role in a gun murder in 2009.

He was one of the first six prisoners hospitalised this afternoon.

The drug used has still not been identified but it is understood to be a powder substance.

It was discovered in at least one cell in a series of searches that took place after the prisoners became ill.

It is understood that inmates who consumed the drug thought it was Spice – a synthetic version of cannabis.

However, they are suspected of ingesting a far more potent substance.

Six inmates were initially brought to hospital while a further four were treated later this afternoon.

Prison sources say that the illicit drugs have been “retrieved” from the C wing and have been sent for testing.

Portlaoise is Ireland’s highest security prison.

In a statement the Irish Prison Service said it is working closely with the HSE and it has secured extra naloxone kits in the event of clinical intervention.

“Extra vigilance is being taken across the prison estate and the Irish Prison Service has commenced an information campaign for prisoners around the dangers of consuming contraband.

“The Irish Prison Service is committed to preventing the access of contraband including drugs into prisons and continues to be a high priority for the Irish Prison Service. The Irish Prison Service has committed to continuing to invest in new technologies and measures to support our efforts to keep contraband out of prisons.

It said prison staff have increased the use of "random and intelligence led cell searches on a daily basis”.

“Our Canine Unit carry out searches around the prisons, including a greater focus on searching deliveries into prisons.

"The Irish Prison Service continues to engage with An Garda Síochána with regard to preventing contraband entering our prison and this happens at both local and national level. The Operational Support Group work closely with their colleagues in An Garda Síochána on a regular basis and the sharing of intelligence has led to target searches resulting in the seizure of contraband.

“The Irish Prison Service are committed to strengthening our measures in keeping drugs out of prison and in this regard a new drug strategy was published last November.”

Gabriel Keaveny, Deputy General Secretary, Prison Officers Association said: “Over the years and at several annual conferences we have raised the issue of overcrowding and illegal smuggling of drugs into our prisons. Despite the best efforts of our members on the ground no significant action has been taken by the authorities to address the drugs issue in our prisons.

“What has regrettably now occurred in Portlaoise Prison was somewhat inevitable”

“This is the second major incident involving illegal drugs in our prisons in three weeks.

“In recent weeks we have had a serious attempt to burn down a Prison Officers home. In recent times we have highlighted the issue of drones delivering drugs, mobile phones and weapons to prisons on an almost daily basis. And we have consistently raised the overcrowding issue, which of course is central to all other issues which emerge in our prisons.

“The Minister and the prison authorities need to see this incident in Portlaoise as an inevitable consequence of inaction over the years. The chronic issues impacting on our prison system must be addressed or we will be confronted with significant crisis events in the very near future, Mr Keaveny said in a statement.

Last month the Irish Prison Service issued an urgent drug alert to all prisons after an analysis by the HSE’s National Drug Treatment Centre confirmed the presence of a nitazene-type substance called N-Pyrrolidino protonitazene - which has been associated with the overdoses in custody.

It is a very strong and potentially deadly synthetic opioid and has been appearing across the country since June.

The tablets often come in blister packs and are often yellow in colour. People could easily mistake them for benzodiazepines.

Today's News in 90 Seconds - August 13th

However, the nitazine tablets do not contain benzodiazepine and are unsafe to use. Nitazine is a synthetic opioid.

The Irish Prison Service sent a protonitazene tablet to the HSE lab after they had an overdose in one jail.

The lab found it was the same type as the one they had begun to see in Ireland since June.