A doctor who was arrested in Berlin in August is now suspected of killing eight patients and in some cases trying to cover up the evidence by setting fires, investigators said Thursday.

The unidentified doctor, who was part of a nursing service’s palliative care team, was suspected at the time of his arrest of killing four elderly patients in June and July and then attempting with mixed success to set fires at their apartments.

Police and prosecutors said Thursday that additional cases surfaced when they examined patients’ files and carried out forensic examinations of suspected victims, two of whom were exhumed.