A nurse and the head of a nursing home in Suita, Osaka Prefecture, were referred to prosecutors Thursday on suspicion of professional negligence in connection with the death of a 68-year-old female resident whose artificial respirator was left turned off.

According to the police, a 53-year-old nurse at Medical Rihabiri Home Kurara Suita allegedly turned off the woman's respirator at around 7:20 p.m. on Aug. 20 to remove her phlegm and forgot to turn it back on, causing her to suffocate.

Although the same thing happened to the same resident in June at the hands of another employee, the 36-year-old manager of the nursing home allegedly failed to report it to her family or the operating firm, Benesse Style Care Co., and failed to take preventive measures, the police said.

Police officials said that artificial respirators are supposed to be kept on at all times but it had become customary at the facility to turn them off when staff needed to remove residents' phlegm.

A nurse who was making her rounds about an hour later reportedly noticed the resident's respirator was not working, and her doctor pronounced the woman dead.

The woman, whose respiratory functions had been reduced by atrophy, had been at the facility since February 2014.

"We let her into the facility because we trusted the staff, but most of the staff did not know how to use the respirator properly and the same accident was repeated," the woman's family said in a statement. "We deeply regret the fact the residents' safety is ignored and the staff was putting priority on the company's profits."

"We take this very seriously and will take measures to prevent a recurrence," Benesse Style Care said.