If from the bond election returns it appears that more than two-thirds of the votes cast in such election were in favor of and assented to the incurring of the indebtedness, the board may, by resolution, at such time or times as it deems proper, issue bonds of the district for the whole or any part of the amount of the indebtedness so authorized, and may from time to time provide for the issuance of such amounts as the necessity thereof may appear, until the full amount of such bonds authorized has been issued.