A nurse serving a life sentence for murdering two patients in northern Germany is now a suspect in at least 84 other murder cases, the BBC quoted the police as saying on Monday.
The 40-year-old, named only as Niels H under German reporting rules, was convicted of attempted murder in 2006 and murder in 2015.
His victims received lethal drug doses at units where he worked.
Relatives of patients who died in clinics where he worked had urged police to investigate further.
A commission was set up in 2014 to investigate the scale of his crimes, which could make him Germany's worst post-war killer.
The medication caused heart failure or the collapse of patients' circulatory systems.
Judges said he was motivated by a desire to win approval by resuscitating the patients he had drugged.
During his 2015 trial, he admitted applying the drug to about 90 people at an intensive care clinic in the town of Delmenhorst.
Police say the abnormalities stretch back to 2000 at another clinic in Oldenburg.

Source: Mena