Purchase of Granted land in Karnataka

Hi All, My name is Kiran and I am in a fix with a agricultural land that my father purchased. The details are below; 1. My father purchased a piece of land in Dharwad (Karnataka) in the year 1974. 2. The EC shows to be clear in titiles and ha all my family members name on it. 3. We wanted to sell this land and made few checks at local (Dharwad) tehisildar's office and found it to be clean, however, upon contacting at the Assistant Commissioner's office, we were given to understand that the land in question has a violation of law while it was purchased. 4. it was told to us that the said land was a "Grant" to the original owner (Date of Grant not known) and should not have been sold to us without converting the few "sharaths" from new to old. 5 now that we have been in possession of the said land from more than 50 years, is there a way out to have this land cleared to our name. 6. we were also informed that Govt. could take possession of the said land whenever it wishes. 6. The original owners are no more and their siblings are not traceable. What could be the possible solution for this?