Ayumi Kuboki, 31, has been arrested on suspicion of poisoning up to 20 patients while she was a nurse at a hospital in Japan

A nurse in Japan has been arrested on suspicion of poisoning up to 20 patients so they wouldn't die on her shift.

Ayumi Kuboki, 31, allegedly poisoned the elderly people by injecting their IV drips with antiseptic solution at Oguchi Hospital, around 20 miles south of Tokyo, in 2016.

Kuboki told police that she hastened the patients' deaths so that they died on another nurse's shift and she didn't have to break the news to their families, newspaper Asahi Shimbun reports.

Nurses at Oguchi Hospital are expected to break the news to families if patients die while they are on duty.

'It would be troublesome if that responsibility fell on me,' Kuboki allegedly told investigators.

Police launched their probe after another nurse spotted bubbles inside the IV drip bag of 88-year-old patient Nobuo Yamaki after he died in September 2016.

Bubbles are an indication that a bag has potentially been tampered with.

Doctors found a high concentration of antiseptic solution in Yamaki's bloodstream and determined that he had died from poisoning.

Kuboki (pictured leaving a police station) allegedly injected the IV drips of elderly patients with antiseptic solution so they would die on another nurse's shift

An autopsy was then carried out on another 88-year-old patient, Sozo Nishikawa, who had shared a room with Yamaki.

The same antiseptic was also found in his bloodstream, and police opened an investigation at the hospital.

Antiseptic was then discovered in the bodies of two further patients, an 89-year-old man and a 78-year-old woman who have not been named.

Police also discovered ten unused intravenous drip bags at the nurses' station tainted with the antiseptic solution.

Investigators found tiny punctures in the rubber seals of the bags, indicating that the antiseptic had been injected into them.

The deaths happened at Ogumi Hospital, around 20 miles south of Tokyo, around September 2016 while Kuboki was working on the fourth floor

When police investigators checked all uniforms worn by nurses in charge of the patients on the fourth floor, they found the antiseptic on only one uniform - that worn by Kuboki - around the pocket.

After her arrest, Kuboki allegedly confessed to killing up to 20 patients, but claimed she targeted only the very sick.

However, police have cast doubt on those claims, saying some of the patients who died during that period were not terminally ill.

Kuboki qualified as a nurse in 2008 and began working at Oguchi Hospital in 2015, where she was known as a quiet but competent employee.

A series of disturbing incidents were then reported on the fourth floor where she worked in 2016, where nurses' uniforms were ripped and drinks were spiked with a foreign substance.

The incidents stopped around August 2016, before the first deaths happened.

Kuboki quit the hospital before she was questioned over the deaths in June, before her arrest on July 7. She has not yet entered a plea.