Forty-six refugees from Ukraine who were placed in emergency rest centre accommodation in Banteer in north Cork on Saturday were treated by medics overnight after complaining of feeling unwell.
It is understood their symptoms included headaches, nausea, dizziness and coughing.
Local doctors and paramedics attended the scene as a precautionary measure.
Covid-19 is not thought to be the cause of the illness with Cork experiencing a surge in cold and flu outbreaks in recent weeks.
Doctors are liaising with the HSE in relation to the outbreak of illness at the facility and medications are being administered to those impacted at the centre.
Cork County Council confirmed the outbreak in a statement: "A total of 46 Ukrainian refugees were placed in emergency rest centre accommodation in Banteer on Saturday night, 16th April.
"A number of refugees complained of feeling unwell upon arrival. Medical assistance was called immediately and medical help was present on site overnight.
"The HSE's Public Health Unit has been mobilised and the centre currently has restricted access while the matter is being addressed."