The New Jersey Department of Health is asking people in certain Mercer County towns to take extra safety precautions when it comes to their household water after an investigation found Legionella bacteria.

In September, samples were collected from 30 homes in Trenton, Ewing, Hopewell and Lawrence -- more than half identified Legionella bacteria in the water samples. It comes after the bacteria was detected in July in several homes in the Hamilton Township area.

Legionnaires is the disease caused by the Legionella bacteria. Legionnaires' disease is a type of pneumonia that people can get after breathing small droplets of water in the air containing Legionella bacteria.

People cannot get Legionnaires' disease by drinking water that has Legionella. Though uncommon, people can get sick when water containing Legionella is aspirated into the lungs while drinking, such as "goes down the wrong pipe.”

Here's how you can protect yourself: Avoid high-risk activities. If you are at an increased risk for Legionnaires' disease, consider avoiding hot tubs, decorative fountains, power washing or similar activities, which may generate increased amounts of aerosols or mist. Also, keep your water heater set to a minimum of 120 degrees.