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Ex-nurse in Yokohama arrested second time on poisoning charge as multiple deaths probed anew

JIJI, Kyodo

In a serial murder case involving a Yokohama hospital, a former nurse has been arrested anew for allegedly poisoning a second patient at the hospital where she once worked.

The suspect, Ayumi Kuboki, 31, allegedly poisoned Nobuo Yamaki, 88, while he was a patient at Oguchi Hospital (now known as Yokohama Hajime Hospital) on Sept. 18, 2016, the Kanagawa Prefectural Police announced Saturday.

The suspect admitted to mixing an antiseptic into Yamaki’s intravenous drip to kill him, the police said, adding that she also apologized.

Kuboki is already under arrest for allegedly killing another 88-year-old male patient, Sozo Nishikawa, in the same way, just two days before Yamaki died, and has already been handed to prosecutors.

Yamaki and Nishikawa were staying in the same hospital room.

In Nishikawa’s case, the Yokohama District Public Prosecutor’s Office said Saturday it has delayed its decision on whether to indict her.

Starting in July 2016 and continuing until Sept. 20 of the same year, 48 patients died at the hospital, including five in a single day in late August and four in one day in early September.

The substances found in their bodies were the same as the disinfectant used at the nurses’ station on the fourth floor of the hospital where the two men were hospitalized.

Among about 50 unused drip bags at the nurses’ station, about 10 were found to have small puncture holes in them. The police believe someone may have used a syringe to inject the disinfectant into the bags.

Kuboki told the police she injected disinfectant into IV bags used to treat about 20 patients, according to investigative sources.

Traces of a surfactant compound were also found in the bodies of three other patients who died. Yamaki died two days after Nishikawa in the same room, and the same type of toxic substance was found in his body and in an intravenous drip bag that had been used to treat him, according to police.

Kuboki has told police she repeatedly injected disinfectant into drip bags, the sources said.