Eight children and one adult were taken to Leighton Hospital this afternoon suffering from minor respiratory symptoms following an incident at Winsford Lifestyle Centre.
The Lifestyle Centre was immediately evacuated following the alert.
Cheshire West and Chester Council will investigate the incident now that the building has been given the all-clear by the Fire and Rescue Service.
Around 56 children from Winsford High Street Primary School were at the centre for swimming lessons. Most were poolside when a small group in the water began coughing.
All 56 were taken to a rest centre set up at nearby Wyvern House for a medical examination and the majority were allowed to go home.
Later it was expected that the children taken to Leighton Hospital would be kept under observation for around four hours as a precaution but none were in a serious condition.
Firefighters have now successfully rescued two men from one of the flats close to the collapse.
Crews remain at the scene.