Tokyo police have searched a psychiatric hospital on suspicion of assaults on patients by four of its medical staff.

Police launched the search of Takiyama Hospital in Hachioji City on Wednesday after being alerted by a relevant party.

Police suspect the four hit patients on the head and in the face last year from January through April.

An investigative source says one of the four, a nurse in his 50s, has already been arrested for allegedly hitting a patient on the head in April.

Police plan to investigate details of the assaults.

Footage obtained by NHK shows a patient in bed speaking, and a person believed to be a medical worker telling the patient not to speak and hitting the person's head.

Other footage shows another medical worker pushing a patient's head against a bed repeatedly, and another hitting a patient's face with a pillow and saying "shut up."

The hospital's homepage says it's a private facility that opened about 50 years ago. According to a report it made in 2021 to the Tokyo Metropolitan Government, nearly 90 percent of its 288 beds are in its psychiatric ward.

The hospital told NHK that it will fully cooperate with the police investigation.