The CBI on Saturday questioned Punjab National Bank (PNB) Managing Director-cum-CEO Sunil Mehta and Executive Director K.V. Brahmaji Rao in connection with the Rs 11,300 crore/$1.8 billion bank fraud case.Both the officials were called at the Central Bureau of Investigation's (CBI) Mumbai branch and were questioned for over eight hours. Mehta and Rao were questioned first time even since the CBI filed the first FIR in the multi-crore scam on February 14 against diamantire Nirav Modi, wife Ami, brother Nishal, uncle Mehul Choksi and his firms Diamond R US, Solar Exports and Stellar Diamond. Nirav Modi, his family and Choksi have left the country earlier in early January. The FIR mentions fraud of around Rs 6,400 crore.The CBI also filed second FIR in the case on February 15 for Rs 4,886.72 crore fraud against the Gitanjali group headed by Choksi.Letters of Undertaking and Foreign Letters of Credit were used to raise and rollover the amount over several years before the fraud came to light following PNB's complaint. Questiong of 12 arrested accused persons continued on Saturday, a CBI official said. On Friday, the CBI also questioned two General Managers and Deputy General Managers of the Mumbai-based PNB's Brady House branch-- the only branch involved in the criminality-- and raided Nirav Modi's Kamala Mills firm and seized some documents.