Lessor sold property without taking NOC from leesee

Sir I am in govt Oil PSU. There are several retail outlets (petrol pumps) whose land is leased to us and we appoint someone else other than landowner as the dealer. In one RO the dealer was terminated for malpractice and we wanted to appoint new dealer. But during getting statutory clearance from district administration, it turned out that some different Person was now owner of land and that the original person (lessor) had sold land to him 2 years back. We have registered lease deed but no mutation found in govt records. The new land owner(person due to whom malpractice was happening) has refused to give NOC to us to run the RO. Also he is influential person. Administration says as per their rules they must habe valid lease/NOC from current landowner and the matter of our registered lease with earlier person is of no concern to us. They also say that if some fraud has been committed then its our lookout. The retail outlet is closed due to this. Monthly rent was being paid through bank to original lessor till this issue came out and he was happily receiving it too. Financial loss is happening and our investment in terms of infrastructure is lying idle What should we do? Our legl cell told us to file case against all 3 i.e. original lessor/current land owner/administration. But original lessor is now untraceble and current land owner(Person responsible for malpractice) is harassing us that due to non mutation this has happened, and instead threatning to lodge case against us to remove our facilities and clear the land. Please guide.