Police in Tokushima City said that a 57-year-old man who was found dead in his hospital bed on Monday was strangled to death.

According to police, the estimated time of death was between 10 p.m. on Jan 26 and 7:30 a.m. the next day at Jonan Hospital, Sankei Shimbun reported. Police said the patient, Tatsuya Kondo, had strangulation marks on his neck. There were no other visible external injuries or signs of resistance.

At around 7:30 a.m. Jan 27, a nurse noticed something was wrong while delivering breakfast and contacted a doctor who confirmed the patient's death at the scene. The hospital called 110 to report that an inpatient had died.

Police said they are analyzing hospital surveillance camera footage to try and find out who went into Kondo’s room prior to his death.

Kondo was in a psychiatric care ward with another patient. On the night of Jan 26, Kondo complained to a nurse that the other patient had stolen his snack. That patient was moved to another room.

Police said he is being questioned along with hospital staff who were on duty overnight.

According to the hospital, there were two nurses on duty and 30 inpatients at the hospital that night.