Section 378F(3) in The Mumbai Municipal Corporation Act, 1888
(3)If no such offer as is mentioned in sub-section (1) is made before the expiration of the said period, the owner or owners of the building shall carry out the demolition provided for by the order before the expiration of six weeks from the last day of that period, or, if the building or such part thereof as is required to be vacated is not vacated until after that day, before the expiration of six weeks from the day on which it is vacated or, in either case, before the expiration of such longer period as in the circumstances the Commissioner deems reasonable, and if the demolition is not so carried out the Commissioner shall cause the building or part thereof to be vacated, if necessary, in the manner provided in section 488-A and take measures to carry out the demolition and sell the materials rendered available thereby.