Three children have been taken to hospital after suffering a reaction at Aura Leisure Centre in Letterkenny, Co. Donegal.
It happened after a children's swimming lesson at the pool this morning.
Staff at the leisure centre evacuated the building and alerted emergency services.
Letterkenny University Hospital put emergency plans in place after the incident became known.
Several ambulances and fire engines attended the scene.
The injuries are not believed to be serious.