The water system and tanks at Hatfield Leisure Centre at Travellers Lane are now being drained and disinfected.

Health experts say there has been no risk to passers-by and the closure is a precautionary measure.

Dr Marion McEvoy, consultant physician in communicable disease control, said: "No cases of Legionnaires' disease have been reported recently in local residents."

Pneumonia risk

She added that fit and healthy non-smokers are rarely susceptible.

"A very precise set of circumstances is required in order for someone to contract the disease, which can give rise to a severe pneumonia requiring hospital admission.

"A susceptible person would need to breathe in a contaminated spray of water droplets of exactly the right size and at the right temperature.

"This happens rarely."

The building will remain closed until further tests have been carried out.