Testing of the 116 cooling towers in the Lenox Hill neighborhood of Manhattan’s Upper East Side found the existence of Legionella DNA in 42 towers (36 percent), according to a fact sheet sent out by the New York City Department of Health and Mental Hygiene (DOHMH). Low levels of Legionella bacteria, which causes Legionnaires’ disease, were found in 24 of the 42.

Testing of the towers was ordered June 16 by the DOHMH after Legionnaires’ disease sickened seven people in Lenox Hill and resulted in the death of a woman in her 90s. After the cluster was first announced, an eighth person took ill and was hospitalized but has since recovered.

Despite the positive tests, the DOHMH has been unable to identify a DNA match between a cooling-tower sample and any of those infected. All towers were disinfected, and towers contaminated with the Legionella bacteria have been cleaned. The city closed its investigation into the outbreak on July 10, according to a DOHMH spokesperson.

New York City receives an average of 200 to 400 reports of Legionnaires’ disease per year. The city’s largest outbreak occurred in 2015, when 12 people died and more than 120 were sickened in the South Bronx. Cooling towers were blamed in that occurrence.