THE BRONX - The death toll in the Legionnaires' disease outbreak in the South Bronx has risen to 10, according to officials. 

The state Department of Health is offering free testing for contamination to building owners.

Mayor Bill de Blasio says 100 cases of the disease have now been reported.  The outbreak is being described by health officials as the largest in New York City history. However, the mayor says no new contaminated sources have been found.

Officials say that the deceased are all older individuals who had underlying medical problems.

Gov. Andrew Cuomo also released a statement Thursday, saying that officials have the matter under control.

Authorities tested 17 cooling towers across the borough, with five testing positive for the legionella bacteria, which causes Legionnaires'.

Health officials say the risk of contracting the disease should decline now that all five towers were remediated. The number of Legionnaires' cases could still rise slightly due to a 10-day incubation period.

Officials are stressing that New York City's drinking water is safe, along with all air conditioning. Legionnaires' cannot be spread person to person, and is treated with antibiotics.

Still, officials are recommending that cooling towers be cleaned. 

Anyone who experiences symptoms of Legionnaires' should immediately head to the doctor. Symptoms include cough, shortness of breath, fever, muscle aches and headaches.