The CBI is questioning four top officials of Punjab National Bank (PNB) in connection with the Rs 11,400-crore loan fraud allegedly pulled off by billionaire jeweller Nirav Modi and his family, sources have said. Two of these officials are at the General Manager-level, while the two others are at the Deputy General Manager-level, the sources added. The agency did not disclose their names as they were not being questioned as suspects at the moment and were only being questioned to understand the intricacies of the scam, the auditing lacunae and the gaps in internal controls that led to the fraud. Sources said the agency is trying to find out how such a big scam could be pulled off by two junior employees without anyone in the bank’s hierarchy becoming suspicious of the transactions for seven years. Sources said the agency is trying to fix responsibility and find out how many more PNB officials or officials of overseas branches of Indian banks could be involved in the scam. “The officials being questioned were at the level of DGM and AGM in the bank when the scam happened. We have seized truckloads of documents and all of them are being studied to reach the depth of the scam and to fix responsibility,” a CBI officer said. He added that the accused and suspects in the case are being confronted with facts recovered from the documents. The agency is also documenting all interrogations and the statements will be later used to join the dots to arrive at a conclusion, the sources said. Meanwhile, CBI officials on Friday conducted searches at one of Nirav Modi’s offices at Kamala Mills in Mumbai. Sources said the agency has recovered “incriminating documents” and are analysing them.