An investigation has begun after an ambulance was called to Upper Hutt's community pool yesterday to treat sick children.
About 15 10- to 15-year-olds experienced irritated eyes and breathing difficulties while at the H2O Extreme aquatic centre.
Eleven patients were later reported to be in a stable condition at Hutt Hospital emergency department.
The slides had been closed after a reading showed high chlorine levels that remained within the maximum safely allowed. The slides reopened when chlorine levels dropped again.
A child reported feeling sick after using the slides and they were closed again, first aid was administered and an ambulance called.