At least a dozen people in New York City contracted Legionnaires’ disease, prompting city officials to launch an investigation into the community cluster to contain it before it becomes a deadly outbreak.

Five people remain hospitalized and seven others were released after being treated for the disease, the New York City Health Department announced on Tuesday. The cases were reported in the last two weeks in Flushing, Queens, and the patients’ ages ranged between early 30s to late 80s. Health officials are investigating two more cases to determine if it was part of the current cluster. There have been no deaths reported.

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Health officials have taken water samples from several cooling tower systems in the area where the cases were reported to test for Legionella, the bacteria that causes the potentially fatal disease.

“As with our previous Legionnaires’ disease investigations, we are in the process of investigating the source of the cluster and are working with building owners in the area to rapidly test and clean cooling towers,” Dr. Mary T. Bassett, city health commissioner, said in a statement.

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Officials urged residents experiencing symptoms such as fever, cough, chills and muscle aches to seek a doctor immediately.

A community cluster of Legionnaires’ disease turned fatal in June when one person died and six others were sickened by the bacteria on Manhattan’s Upper East Side. Another Queens resident died in September after contracting the disease.