Filed FIR for Forgery & Fraud, Police not acting

In 1968, my father and his five friends bought six kanals of land and carved out six plots. Mutation was done. In 2010 we (brothers) found that someone had constructed a factory on our plot. When asked, he revealed that someone had sold land to him based on a POA executed by one of the five friends of my father. We found that the POA was executed five years after the supposed executant had died: death certificate from municipal corporation attests to this fact. Additionally, while the dead man owned less than one kanal, as per mutation, he had executed POA for 4 kanals. We filed FIR and attached all documents - death certificate, demarcation certificate by Patwari & Tehsildar, etc. Police has done nothing for five years and wrote that the case was pending because we have to be present for demarcation. Since we live in distant places, and are senior citizens, we are unable to be physically present. In fact we are not able to pursue even the civil suit that we had filed. Is police not supposed to pursue the case on its won, more so because the demarcation certificate has been submitted when FIR was filed?