A nurse at a Tokyo municipal hospital accidentally injected disinfectant into the intravenous drip of a patient instead of a substance meant to prevent blood clotting, killing the woman in February, police said Tuesday.

Police have launched a manslaughter investigation involving the nurse at Tokyo Metropolitan Hiroo Hospital, Shibuya Ward. Police also suspect hospital management oversight.

The patient, a 58-year-old homemaker from Urayasu, Chiba Prefecture, was suffering from rheumatoid arthritis and was hospitalized Feb. 8. She underwent an operation on the middle-finger joint of her left hand two days later.