Mich. Comp. Laws § 123.369

Sec. 9. Any city or village issuing bonds pursuant to the provisions of this act may, at the time of the authorization of such bonds, provide by ordinance for the issuance of additional bonds of equal standing in the event the bonds first authorized shall prove insufficient or in the event subsequent extension, enlargement, improvement and/or repair is deemed advisable, which said additional bonds may be negotiated from time to time as the proceeds therefrom may be necessary for such purposes.