A technician holds a culture dish with colonies of legionella in a laboratory. (Reuters)

NEW YORK –  A third person with Legionnaires' disease has died as New York City investigators search for the source of an outbreak that has sickened dozens.

A spokesman for Mayor Bill de Blasio says 11 more people have been hospitalized in the South Bronx since Thursday.

On Friday, investigators found legionella bacteria at the Opera House Hotel in the Bronx. Previously the bacteria had been found in equipment at a local hospital and a complex that contains a movie theater.

De Blasio spokesman Peter Kadushin says the third person killed was a middle-age man with prior health conditions. The man had been hospitalized.

Legionnaires' disease is caused when water tainted with a certain bacteria is inhaled into the lungs. There have been 2,400 cases nationwide this year and more than 130 in New York.