A German male nurse jailed for life two years ago for killing two patients with lethal drug overdoses is now a suspect in at least 84 more murders, police said Monday.

Niels Hoegel, 40, was jailed in February 2015 for two murders of intensive-care patients at the Delmenhorst hospital near the northern city of Bremen.

Police said Monday that investigators exhuming and analysing more bodies had so far found evidence of "84 more murders", which would make him one of Germany's worst ever serial killers.