An 8-year-old patient at a Tokyo hospital for children with mental disorders drowned last week while taking a bath because the hospital worker who was supposed to care for the girl was absent, it was learned Monday.

Police started probing the death of the patient at Tokyo Metropolitan Umegaoka Hospital as a suspected case of professional negligence resulting in death.

According to the police probe and explanations by the hospital in Setagaya Ward, Tokyo, the girl was found submerged in the bathtub around 1:30 p.m. Friday. She was taken to another hospital for emergency treatment but was pronounced dead Saturday.

A 45-year-old female care worker had the girl and another female patient take the bath together from shortly before 1 p.m. Friday, and left the bathroom to take part in an event in a different room.

The girl apparently drowned after the other patient left the bath. A manual requires that at least two care workers be present when a patient bathes.

Initially, the care worker and a nurse planned to have the girl take the bath from 1:30 p.m. But the care worker alone took the patient to the bathroom because she moved up the schedule in response to a request from the girl, according to the hospital.