A special court here today extended till March 17 the CBI custody of former Punjab National Bank DGM Gokulnath Shetty in connection with a case related to diamond trader Mehul Choksi's firms in the multi-crore PNB fraud case. Shetty was arrested on March 6 in connection with Choksi's case. Earlier, he was in CBI custody till March 3 in connection with diamantaire Nirav Modi's case in the PNB scam. Modi's firms allegedly defrauded PNB of over Rs 6,000 crore and Choksi's firms Rs 7,080 crore.