The results of toxicology test results are due after two students took ill in Galway yesterday.
Both were taken to University Hospital Galway for treatment.
It is understood that their conditions improved overnight and one of those treated has since been discharged from hospital.
NUI Galway said its emergency response protocol was activated when the two students needed medical care, after taking ill on campus.
It has asked students and staff to report any bad reactions to any substances that may be circulating.