Prior to the completion of all public health facilities described in Section obligation of authority; reimbursement to counties; refinancing or refunding of obligations” class=”unlinked-ref” datatype=”S” sessionyear=”2020″ statecd=”AL” title=”22″>22-3A-19, any portion of the principal proceeds derived from the sale of the bonds which the board of directors may determine is not then needed for any of the purposes for which the bonds are authorized to be issued shall, on order of the authority, be invested by the State Treasurer in permitted investments which mature at such time or times as the authority shall direct. At any time and from time to time on order of the authority, any such investments may be sold or otherwise converted by the State Treasurer into cash. The income derived from any such investments shall be applied first for the payment of the costs of providing the public health facilities described in Section 22-3A-19 and, to the extent not needed for such purpose, such income may be disbursed on order of the authority for any purpose for which the authority may lawfully expend its funds.