A child is in a serious condition after pool chemicals caused some swimmers to experience respiratory issues at Wollondilly Leisure Centre Monday morning.
Nine children and one adult were treated for mild to moderate breathing problems, a NSW Ambulance spokesman said.
The spokesman said four people had been transferred to hospital, including one child to Campbelltown Hospital in a serious condition.
He said three other children and one adult were in a stable condition and transferred to Campbelltown and Bowral hospitals.
A Fire and Rescue NSW spokesman said pre-mix chemicals added to the centre’s indoor swimming pool caused some swimmers to experience respiratory issues.
The FRNSW spokesman said the chemicals caused a “gas cloud” at the centre.
He said water and ventilation testing was underway and the indoor swimming pool remained temporarily closed.
FRNSW, ambulance and police remain at the scene.
The pool is expected to remain closed until Monday afternoon.