The man, who worked at clinics in Würselen and Cologne, was sentenced to life imprisonment last year.
So far, 39 bodies have been examined as part of the new investigation, the Aachen prosecutor's office told the German news agency DPA.
According to the verdict, the nurse gave dangerously large doses of sedatives to seriously ill patients between December 2023 and May 2024. The motive was, among other things, to reduce his workload during night shifts, according to prosecutors.
The investigation now focuses on possible murders that may have been committed before this period, as the man has worked at the clinic in Würselen since 2020.
