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The health department in Australia's Victoria state is working to track down the source responsible for the legionnaires' disease outbreak in Melbourne, Premier Jacinta Allan said on Thursday.

Allan warned the number may be above the 60 confirmed cases, and urged the people who were feeling unwell with symptoms like chills, fever or cough to seek medical help.

The premier confirmed that the health officials were testing and cleaning cooling towers as they checked for a contaminated water source, which may be responsible for the legionnaires' disease outbreak last week, reported The Guardian.

"As people are presenting with the illness, thorough testing is being undertaken and those tests take a number of days to go through processing," she said. "It is helping to identify a geographic range ... around the north-west of the city. Further work is being undertaken to pinpoint precisely that location and advice will be provided [when it is available]."

According to the Victorian Department of Health, most of the confirmed patients were in their 40s, who have been admitted to hospitals, Sky News reported.

The health department has also warned that "most cases are arising in people who are normally at greater risk of the infection, however, there are also cases in otherwise active and normally healthy adults."

Smokers, and anyone with chronic lung disease or poor immune system also were at risk of being infected, the Victorian health department has warned.

The process to confirm the legionnaires' disease takes about five to seven days, which is why people are being asked to get immediate medical care if they feel the symptoms.

"People who present with the illness provide tests – they take between five to seven days to be processed," Allan said. "That is why a very strong precautionary message is to be delivered around people who may have been in that broader geographic exposure area to go and seek medical attention if they feel that they have those symptoms that can be quite debilitating."

The disease was caused by legionella bacteria, found in water bodies, either natural or artificial, and the infection was spread when a person breathed the fine droplets of water that contained the bacteria.

In 2000, four persons died and 150 fell ill when the Melbourne Aquarium cooling towers became infected with legionella pneumophila bacteria.