Japanese police have sent papers to prosecutors on seven people employed by a city near Tokyo for allegedly falsifying a document to admit a man to a controversial psychiatric hospital. The institution is currently under investigation for allegations of multiple workers assaulting patients.

Investigative sources say the seven individuals are former and current officials at Tokorozawa City. They are suspected of being involved in the process to hospitalize a man in his 50s in Takiyama Hospital, located in Tokyo's Hachioji City, in 2018.

The sources say the seven created a false document saying they could not communicate with the man's sister in the process, even though the law requires the family's consent.

A lawyer for the man says having contact with his sister was possible at that time.

Police opened an investigation in March, following a complaint from the man.

The sources say the seven suspects told investigators that it is true they could not contact the sister. They are also suspected of making him unable to leave the hospital for a long period.

Police also referred some former hospital employees to prosecutors for their suspected involvement in the man's confinement.

Three nurses of the hospital have been slapped with a summary indictment on charges of assaulting patients.