German police said that a doctor is being held in Berlin after two patients were found dead in his psychotherapy clinic and several more were hospitalized with signs of poisoning.

Spokesman Karsten Mueller of the Berlin police said that they received an emergency call Saturday evening after the doctor met with 12 patients.

Mueller added that the dead are two men, 28 and 59 years old. Their names have not been released.

According to him, one person remains in a coma in critical condition while the other patients are improving and being released from the hospital.

Police do not know what the patients were given, but are expecting the results of autopsies on the two dead.

The 50-year-old doctor has not been named.

In Germany, psychotherapists are required to have a medical degree. Psychotherapists employ a range of techniques based on experiential relationship building, dialogue, communication, and behavior change that are designed to improve the mental health of a client or patient, or to improve group relationships.