Unless he was admitted pursuant to the Interstate Compact on Mental Health as set out in § 44-25-20 or a supplementary agreement thereto, if any person admitted to a State mental health facility is not a citizen of this State, the superintendent of the facility concerned shall immediately notify the Department of Mental Health, and the Department of Mental Health shall notify the mental health commission or other appropriate agency of the state of which the patient or trainee is a citizen. If the state of his citizenship fails to provide for his removal within a reasonable time, the Department of Mental Health shall cause him to be delivered to the officials authorized by law to care for similar persons pending their commitment to state institutions of the state of his citizenship. The cost of these proceedings and conveyance from this State shall be borne by this State under reciprocity agreements made by the Department of Mental Health with the mental health authorities of other states. In entering upon such reciprocal agreements with other states, the Department of Mental Health shall provide that the requirements necessary to gain residence in this State shall not be less than those required for the acquisition of residence in the other contracting state. The Department of Mental Health may, however, in cases of undue hardship waive the requirements of residence, for cause.