Serial killer suspected of poisoning 48 elderly patients at Japan hospital

Police believe suspect may be an insider with medical knowledge

Police are investigating whether the victims' intravenous drips were poisoned (iStock)

Police in Japan are investigating whether a serial poisoner is responsible for killing as many as 48 elderly patients by injecting disinfectant into their intravenous drips.

Suspicions began after an autopsy showed two elderly patients had been poisoned in Oguchi Hospital, Yokohama.

Sozo Nishikawa and Nobuo Yamaki, both 88, died on 18 and 20 September respectively, after having a drip administered.

Two elderly patients were poisoned at Oguchi Hospital, Yokohama (Google Maps)

Investigators found 10 unused intravenous drip bags with small holes in their rubber seals on the fourth floor of the hospital, where the two elderly patients had died, The Japan Times reports.

Police believe the suspect may be an insider with medical knowledge.

They are now also investigating the deaths of 46 elderly patients since July, who were being treated on the same floor as the two deceased men.

Hospital staff told the newspaper there had been no outbreaks of infection which could account for the deaths.

The two patients died around a lightly staffed three-day public holiday. The entrance to the hospital was locked and guarded at night.

Last month, a staff member’s lips became blistered after they consumed a drink that may have been laced with bleach, The Japan Times said in another report.

It is unknown whether the incidents are related.

The investigation comes two months after the killing of 19 people at a facility for the disabled near Tokyo.