If an individual ordered to be hospitalized pursuant to section four of this article is eligible for hospital care or treatment by any agency of the United States, then, upon receipt of a certificate from such agency showing that facilities are available and that the individual is eligible for care or treatment therein, the circuit court or mental hygiene commissioner may order him to be placed in the custody of such agency for hospitalization. When any such individual is admitted pursuant to the order of such circuit court or mental hygiene commissioner to any hospital or institution established, maintained or operated by any agency of the United States within or without the state, he shall be subject to the rules and regulations of such agency. The chief officer of any hospital or institution operated by such agency and in which the individual is so hospitalized shall, with respect to such individual, be vested with the same powers as the chief medical officers of mental health facilities or the director of health within this state with respect to detention, custody, transfer, conditional release or discharge of patients. Jurisdiction is retained in the appropriate circuit court or mental hygiene commissioner of this state at any time to inquire into the mental condition of an individual so hospitalized, and to determine the necessity for continuance of his hospitalization, and every order of hospitalization issued pursuant to this section is so conditioned.