A public swimming pool has been closed after a man was admitted to hospital suffering from Legionnaires' disease, health chiefs said last night.

No details have been released about the man other than that he is from Lanarkshire and he is detained in hospital. His condition was said to be "stable and improving" last night.

An investigation to identify the possible sources of his infection is being carried by NHS Lanarkshire's Public Health Department, environmental health officials from South Lanarkshire Council, the Health and Safety Executive, and Health Protection Scotland.

GPs in the area have also been made aware of the situation. Health officials said the wet facility at Hamilton Water Palace, including the swimming pool, its flumes and sauna facility, was closed yesterday as a precautionary measure following testing of its handwashing and shower facilities. The wet facility is expected to reopen today.

Dr John Logan, NHS Lanarkshire's consultant in public health, said: "Legionnaires' disease is caused by the bacterium legionella and usually has an incubation period of two to 10 days. It normally presents with flu-like symptoms, followed by pneumonia, and sometimes with diarrhoea and confusion.

"Patients usually respond well to treatment with certain common antibiotics."

Dr Logan advised members of the public who are concerned that they may have symptoms of the disease to contact their GP or phone NHS 24.

Legionnaires' disease is a potentially fatal form of pneumonia. The bacteria which causes it can be found in air conditioning systems, cooling towers, spas and Jacuzzi baths. However, illness only occurs when water containing the bacteria becomes airborne water droplets. It is not passed from person to person.

It can be fatal, especially in those who are particularly vulnerable, such as the elderly or those with chronic diseases.

There were 32, 33 and 42 cases of legionella reported in 2004, 2005 and 2006 respectively to Health Protection Scotland. The majority of cases are diagnosed in returning travellers.