Officials are investigating the circumstances surrounding this month's deaths of two patients and infections of four others, all of whom apparently contracted Legionnaires' disease at St. Peter's University Hospital in New Brunswick, N.J.

In all, three men and three women have been diagnosed with the disease, a type of pneumonia that can be fatal for those with weakened immune systems. Test results were pending on five others. All six patients who tested positive were being treated for other serious illnesses at the time, a state health official said Wednesday.

A drop in the amount of chlorine used to kill the bacteria in the hospital's water system may have caused the outbreak of Legionnaires' disease. The bacteria that causes it can be spread through plumbing and air-conditioning systems. It was first identified after a deadly outbreak at a 1976 American Legion convention in Philadelphia.

- AP