Police have launched a malpractice investigation after a hospital in Handa, Aichi Prefecture, reported Sunday that an elderly woman died in an accident there, police officials said Monday.

The 82-year-old patient was hospitalized for gallstones at Handa Municipal Hospital. According to the officials, the hospital put a feeding tube into her stomach through her nose last Tuesday after she lost her appetite.

On Sunday morning, a 28-year-old surgeon on duty replaced the tube after a nurse found it had come off at 6 a.m.

But at around 12:30 p.m., the patient complained of chest pains when another nurse put warm water into the tube.

Doctors found through X-rays that the replaced tube was actually put into her left lung.

Seven doctors and nurses, including the surgeon, treated the woman with procedures that included a lung washing, but she died of acute lung damage caused by foreign matter in the lung at around 6:25 p.m.

Police said they will order a judicial autopsy to determine whether the death was caused by the tube or the warm water.

Hitoshi Hidano, vice chief of the hospital, said Monday that the hospital is sorry about what happened and will offer an apology to the patient's family.