Up to five people are being treated at Letterkenny University Hospital following an incident at a leisure centre in Co Donegal.
At least three children were taken to hospital after the incident at the Aura Leisure Centre in Letterkenny.
It is understood the children became unwell during a swimming lesson this morning.
The pool was evacuated by the staff at the centre and emergency services were notified.
A number of ambulances and fire brigades attended the scene.
Doctors and nurses were also on site at the centre where treated the children for injuries which are not believed to be serious.
It is also understood a consultant in emergency medicine attended the scene, before the people were taken to hospital.
In their statement following the incident, Aura Leisure Management explained that backwash, which leaked into the pool, caused some cloudiness and gave rise to foul odours.
"In line with our safety procedures, as a precautionary safety measure, we evacuated the pool and notified the emergency services to ensure that every person in the pool was checked for any reactionary medical issues.
"While today's response might be criticised as an overreaction to the cloudy water conditions, it is reassuring that the Emergency Services and the Hospital share our 'safety first' policy.
"It's better to be safe than to be sorry".
Additional reporting Sharon Tobin