Tenancy rights in collapsed building

My family were occupants(tenants under pugree system) in a building which collapsed approx 50 years ago due to rains. After the building collapsed we moved off from there as only the ground floor was standing. All my family members are living as of now and want to know how to claim rights there. As of now, there is only a board put up stating it belongs to a coop hsg society and trespassers will be prosecuted. There is no constructions going on over there. Only patras and bamboos are put up, demarcating the plot of land. Original Rent receipts and ration card is available as proof of occupancy. Your advise in this matter will be very helpful