815 prisoners at the Midlands Prison in Portlaoise are being tested for Covid-19 alongside staff after it was confirmed that five inmates have tested positive for the virus and are receiving treatment.
The outbreak in the prison is the first such outbreak in an Irish prison since the beginning of the pandemic.
There have been five other prisoners who tested positive for Covid-19 but they had all tested positive before they arrived in prison.
In a statement, the Irish Prison Service said the five prisoners have been isolated in line with infection control procedures and contact tracing is ongoing.
The positive cases relate to one area of the jail and all prisoners accommodated in this section and staff who are assigned to this area have been tested, the statement added.
All other prisoners and staff in the Midlands Prison are being tested as a precaution.
The Irish Prison Service said an outbreak control team meeting has taken place to review the cases and agree the actions to be taken to mitigate against further possible spread of the disease within the facility.
There were no cases reported in the prison during the first wave of the coronavirus.