Bangalore Development Authority [Bda] — Illegal encroachment of my site

I bought a BDA site in 2006 and have been paying the taxes regularly. But now the site is illegally encroached by some local guy who claims to be his land and he had never sold it to BDA. I have registered a complaint with the BDA and no action is taken by them inspite of they having all the details and are fully aware of the encroachment of a total of 6 acres in II Block, JP Nagar 8th Phase - The authorities give all kinds of excuses including saying that one of their department who has to approve the file returned it without signing.