An investigation was opened after an ambulance was called to the Upper Hutt community pool yesterday to treat sick children.
About 15 children aged 10 to 15 experienced symptoms of eye irritation and difficulty breathing at the H2O Extreme Aquatic Center.
Eleven patients were subsequently reported in stable condition to the emergency department at Hutt Hospital.
The slides were closed after a reading showed high levels of chlorine which remained within the safe maximum allowed. The blades reopened when the chlorine levels dropped again.
A child reported feeling unwell after using the slides and they were closed, first aid was given and an ambulance was called.
The building was then cleared as a precaution.
Worksafe said the most likely cause was lack of ventilation in the slide area, as well as heavy use of the slides, but further investigation was needed.
Upper Hutt City Council said there had been no spills or leaks of chemicals.
Council’s director of community services, Mike Ryan, said the incident was deeply regretted.
“Our hearts go out to the children and their families who were affected yesterday afternoon,” Ryan said.
The pool is open again today, but the slides will be closed while further investigations take place.