New York City health officials are continuing to investigate a cluster of Legionnaires’ disease, a serious bacterial lung infection, where the number of cases has risen to 73, including three deaths.

Three people have died and at least 67 people have been diagnosed with Legionnaires’ disease in a cluster that broke out in New York City last week.

The cases are most likely linked to a cooling tower in central Harlem, health officials said. More than 60 people have fallen ill, including three people who have died, from Legionnaires’ disease in New York City over the past several weeks, according to the city’s health department.