Two Scarborough residents and a recent visitor to the area, who all became ill last month, had contracted the bug, laboratory tests have indicated.

Both visitors received treatment and have now made a full recovery, but the third patient died in Scarborough Hospital.

However, it was found that although the patient had Legionnaire's disease, it was not the cause of death in this case.

The source of the outbreak also remains unknown despite a rigorous investigation by a number of health agencies.

Dr Autilia Newton, director for North Yorkshire and the Humber Health Protection Unit, said: "Our condolences go to the family of the patient who has died at this very sad time.

"Thorough investigations have been carried out by North Yorkshire and the Humber Health Protection Unit, North Yorkshire and York Primary Care Trust, Environmental Health at Scarborough Borough Council and the Health and Safety Executive to investigate whether any possible common source of infection exists between the three cases.

"However, as is common when multiple cases of Legionnaire's disease are confirmed, a source has not been identified."

GPs across Scarborough have been informed and asked to be vigilant for people with symptoms which could be Legionnaires' disease, but no further cases have been notified.

Dr Newton added: "Legionnaires' disease is a bacterial disease which may cause pneumonia. It is spread through the air from a water source.

"Person to person spread does not occur.

"Breathing in mist from a contaminated water system is the most common means of transmission.