The New York City Department of Health is tracking an outbreak of Legionnaires' disease that killed two people and made 31 others ill in the South Bronx.

The department said Wednesday that the newest wave of the pneumonia has been recorded since July 10 and it is now trying to find the correlation between the deaths and the outbreak, according to FOX News.

The current outbreak has double the amount of cases recorded as the last outbreak, when 12 people in the Bronx fell ill in December 2014. Officials traced the source of contamination to cooling towers at Co-op City, the world's largest cooperative housing development.

As reported by the Centers For Disease Control and Prevention, the disease is caused by the bacteria Legionella that can be found in various plumbing systems. It is spread by breathing in mist from water but can't be spread from person to person. While the illness is usually found in the summer and early fall, it can occur at any time of the year.

Symptoms for Legionnaires' include fever, cough, chills and muscle aches, according to Reuters.

Most of the cases have been reported from the South Bronx neighborhoods of Highbridge, Morrisania, Hunts Point and Mott Haven, officials said.

"We are concerned about this unusual increase in Legionnaires' disease cases in the South Bronx," Health Commissioner Dr. Mary Bassett said in a statement, according to the Wall Street Journal.

Bassett said officials are "concerned about this unusual increase" in cases in the South Bronx. She described the outbreak as an "evolving situation in which the numbers may change."