City officials say a third person has died after contracting Legionnaires' disease in the South Bronx.

The number of cases also increased from 46, which was reported yesterday, to 57. Forty-two of the people diagnosed with Legionnaires' disease since July 10 were hospitalized. Nineteen of those treated have been discharged, Newsday reported.

The latest victim has "additional underlying medical problems," CBS reported. The other two people who died from the disease suffered from other health issues as well.

"We will continue to be vigilant on all fronts, ensuring the health and safety of New Yorkers by both addressing Legionnaires' at its source, and ensuring affected New Yorkers who need it are getting proper treatment," Mayor Bill de Blasio said in a statement.

De Blasio and Health Commissioner Dr. Mary T. Bassett announced Thursday that city officials are overseeing the cleaning of the cooling towers at Lincoln Hospital and Concourse Plaza, and the Opera House Hotel, which are thought to be sources of Legionnaires' disease outbreak in the South Bronx, CBS reported.

The Health Department is also testing other possible sources and will order decontamination of any additional sources. They are testing 10 additional sites surrounding the affected area and interviewing patients and reviewing records to determine whether cases share a common exposure.

Legionnaires' disease is a severe form of pneumonia that is caused by the bacteria Legionella. New Yorkers with respiratory symptoms, such as fever, cough, chills and muscle aches, are advised to promptly seek medical attention. Symptoms of the disease also include headache, fatigue, loss of appetite, confusion and diarrhea.

Symptoms usually appear two to 10 days after significant exposure to Legionella bacteria. Most cases of Legionnaires' disease can be traced to plumbing systems where conditions are favorable for Legionella growth, such as whirlpool spas, hot tubs, humidifiers, hot water tanks, cooling towers, and evaporative condensers of large air-conditioning systems.

"As we continue to investigate the potential sources of this cluster, we remind New Yorkers that this is a very treatable disease and we urge anyone who might be experiencing symptoms of Legionnaires' disease to seek medical attention immediately," Bassett said in a statement released Thursday.