25 children were exposed to airborne chemicals at a swimming pool in Co Kildare earlier today.
The schoolchildren were swimming in NUI Maynooth when chemicals used near the water entered the ventilation system.
19 children returned to their school with 6 children remaining in hospital as a precautionary measure.
The vent system was switched off and all of the children were examined by a GP at the scene.
A HSE spokesperson said 15 ambulances are at the scene and the children are being transferred to Crumlin and Tallaght Hospitals "as a precaution".
A member of the Maynooth Educate Together team said: "shortly into the lesson, the staff noticed that the children were coughing … quite suddenly they had begun coughing.
"Some of them were nauseous and complained of being short of breath … [they] were evacuated from the pool very very quickly."
The University confirmed the incident happened at about 10.30am this morning "when vapour from the swimming pool’s plant room entered the air conditioning system during a maintenance operation."
It said both the University and the Health and Safety Authority were investigating.