resale flat in Chennai with deviation in constructed area

Sir, I am planning to buy a resale flat of 3 years old in Annanur, Chennai. On verifying the documents, it was found that the builder has constructed 955 sft flat whereas approval is for 600 sft in ground floor. The fsi is 1.29 as per approval whereas the builder has constructed around 5600 sft on 2457 sft land area. As per this, the fsi comes around 2.4... clearly violation. When I raised with seller and builder.. they were telling that hdfc loan was sanctioned for this flat and bankers have approved the project and the builder further said that in Chennai 70 to 80% flats are constructed by deviating the apProvals and if cmda has to demolish these flats.. then 80% of flats in Chennai should be demolished and also said that bankers also are aware of this problem.. the builder said nothing will happen as they paid huge bribes to all the sanctioned authorities like cmda, panchayat, electricity, town planning, etc.. Please advice whether to buy or not as the said flat is presently under loan with HDFC. Regards Krishnan