A second person has died in connection with an outbreak of Legionnaires’ disease in New York City, the New York City Health Department announced Saturday. The outbreak, concentrated on Manhattan’s Upper East Side, has now infected 72 people, according to health officials.

The first death was reported Friday, and the second fatality was announced the following day. "We are heartbroken to learn that another New Yorker has lost their life to Legionnaires’ disease on the Upper East Side. Our deepest condolences are with their loved ones as they grieve," New York City Health Commissioner Dr. Alister F. Martin said in a statement.

Legionnaires’ disease is a severe form of pneumonia caused by a type of bacteria that thrives in warm, stagnant water. Health officials are testing cooling towers, which are components of large building air conditioning systems, as potential sources of the bacteria. Property owners have been instructed to drain and disinfect any towers that test positive for the bacteria.

While health officials have not identified a definitive source for the current outbreak, they noted a sustained decline in new cases. This decrease suggests that the source of exposure to the Legionella bacteria has likely been removed. Legionnaires’ disease is treatable, but complications can be fatal for approximately 10% of those infected, according to the U.S. Centers for Disease Control and Prevention.

Last year, a separate outbreak of Legionnaires' disease in New York's Harlem neighborhood resulted in seven deaths and sickened more than 100 people.