Land plot usurped. Need help.

Hi all,

My father had bought a land plot in Greater Noida near Pari Chowk back in 2008-09. When he visited the plot 3 days back (after a long time), he found that a certain relative of the person who originally sold this plot to my father has built a one storey building on the plot.

My father has filed an FIR in the nearby police station. He also found out that even though my father has the registration deed, that person has updated his name in the Dakhil Khariz (mutation) department as the legal owner of this property. My brother is trying to figure out where our Dakhil Khariz document is and will send the scan of it to my father ASAP. My brother and I are currently not in NCR area.

Is it even possible to do this mutation without him having shown the registration of the plot in his name? I really need some legal help in this. Can anyone please help or advice how to proceed?

Update : It seems that dakhil kharij and the registry that was done by my father was for a single plot in a khasari. However, this guy went ahead and registered + did khariz dakhil for a larger plot in that khasari, some part of which is my father's plot and the other part is an undemarcated piece of land that is part of that khasari but was yet unregistered. That is why the land revenue officials could not figure out that the culprit is doing registry of a land, part of which is already registered and mutated.