AUGUSTA, Maine (AP) The Maine Center for Disease Control and Prevention is investigating a cluster of six Legionnaires’ disease cases in the Bangor area.

The CDC said Friday health care providers have diagnosed about one case in each month since last November, and officials are trying to determine if they’re related. The CDC said all six individuals were hospitalized and that one died, although it’s unclear if the Legionella bacteria was to blame.

Legionnaires’ disease is a severe form of pneumonia caused by inhaling water droplets containing the bacteria. The bacteria is common in streams and ponds, but it can also spread in buildings through air conditioning systems, hot tubs and fountains.

Last year, there were 33 cases in Maine. The exact number is uncertain because healthy people generally don’t produce symptoms.