A total of 11 prisoners are being treated at the Midlands Regional Hospital in Portlaoise following a major incident yesterday afternoon — just weeks after the Irish Prison Service issued a nationwide alert about deadly drugs circulating in the prison estate.

The Irish Penal Reform Trust (IPRT) has said overcrowding is contributing to drug problems in prisons.

Portlaoise Prison was at 107 per cent capacity yesterday.

IPRT executive director Saoirse Brady told RTÉ: “There is a health-led approach in the community to substance misuse, and the emphasis should be on that within the prison estate as well, taking into account the security considerations that are there.

“Drug use in prison does happen and a zero tolerance approach doesn’t always work.”