BERLIN (AP) — German prosecutors say they're investigating the operator of a clinic near the Dutch border that offers alternative cancer treatment on suspicion of negligent manslaughter and bodily harm after three people who were treated at the facility died.

Prosecutors in Krefeld said Friday the man appears to have treated five people with the compound 3-Bromopyruvate, which isn't officially licensed as a medicine, between July 25 and 27, news agency dpa reported. Three of the five treated at the clinic in Brueggen-Bracht, two from the Netherlands and one from Belgium, subsequently died, and two Dutch women were hospitalized.

Prosecutors said investigations haven't produced evidence that the suspect deliberately set out to kill or harm patients. It also remains unclear whether the patients' deaths were directly related to the substance used.