6.(1) Whenever a declaration has been made and public notice thereof has been given under section 3, it shall, subject to the provisions of sub-sections (2) to (4), be lawful for such officer as the Government may, by general or special order, authorize in this behalf, and for his servants and workmen, to enter and demolish any buildings or other constructions on the surface, to cut down or grub up all or any of the trees, to remove or alter all or any of the banks, fences, hedges and ditches, to make underground and other drains, to fill up all excavations, and demolish all buildings and other constructions below the surface, and generally to level and clear the said land and do all such acts for, leveling and clearing the same as he may deem necessary or proper, but in such manner nevertheless that evidence of the boundaries of the lands held by different owners may be preserved. (2) The powers conferred by sub-section (1) shall not be exercised,- (a) save as otherwise provided by sub-section (3), before the making of the award hereinafter referred to in section 12, nor (b) save as otherwise provided by sub-section (4), after the expiration of six months from the making of the said award, or any shorter period on the expiration of which the officer exercising such powers gives notice to the Collector that there will be no further exercise of them. (3) In case of emergency, the Government may, by notification in the official Gazette, declare that all or any powers conferred by sub-section (1) may be exercised at any time within six months after the publication of the notice referred to in section 3, sub-section (2), and such powers may be exercised accordingly, and the said notification shall be conclusive proof of emergency. (4) Nothing in sub-section (2) shall be deemed to preclude any such officer or his servants or workmen from exercising at any time the said powers for the purpose of removing, wholly or in part, any building or other obstruction maintained, created, added to, altered, planted, stacked, stored or otherwise accumulated in contravention of this Act or of any rule or order made thereunder or of any condition prescribed in accordance therewith.