Precautions to identify and sell land

Respected Experts, I write this to seek your guidance in the following: My parents who are no more now had some agriculture lands near chennai. They have sold one by one in the past (prior to 1960). On perusal of the old documents I observed that an area of 51 cents seemed to be not sold. I applied for E.C. for the Survey No. and found my guess is correct. However me or my known circle of relatives/ friends could not identify the exact location of the land, since the agriculture activities were stopped long back in the area. When I contacted the VAO of the village, he says the village "adangal" does not show any land in my parents' name. This creates a doubt whether there may be error in the E.C. given.For this reason I do not want this handled by the political persons, fearing they may create documents / patta , and I may be caught for any wrong doings. As the value of the land may be more now I do not want to leave this. Kindly guide me as to how to proceed, and whom to and how to approach safely in this regard. Thanks & Regards J. Giridharan