The board of directors, if it deems it not for the best interest of the district that the lands mentioned in the petition, or some portion thereof, should be excluded from the district, shall order that the petition be denied; but if it deems it for the best interest of the district that the lands mentioned in the petition, or some portion thereof, be excluded from the district, and if no person interested in the district shows cause in writing why the lands or some portion thereof should not be excluded from the district, or if having shown cause withdraws the same, and also, if there are no outstanding bonds of the district and no contract between the district and the United States, then the board may order that the lands mentioned in the petition or some defined portion thereof, be excluded from the district.