CHICAGO (CBS) — The Illinois Department of Public Health is investigating two cases of Legionnaires’ disease in two people who were patients at Rush Oak Park Hospital.

One person was a patient in May and the other in mid-July, the department said in a statement. Both were patients at the hospital during the time when they could have been exposed to the bacteria.

IDPH sampled the facility’s water this week, and previous water samples collected by the hospital showed results positive for Legionella bacteria.

According to the release, the hospital said it routinely conducts water testing and has taken steps to reduce potential exposure, including adding disinfectant to the water, flushing pipes and installing point-of-use filters.

The hospital is also working to identify other potential cases and ensure appropriate testing.