The fraud-hit Punjab National Bank (PNB) has reported an additional Rs 1,300 crore unauthorised transactions, taking the estimated quantum to Rs 12,600 crore in the scam related to diamond trader Nirav Modi and owner of Gitanjali Gems, Mehul Choksi.In a 11.22 p.m., late night filing with the stock exchanges on Monday, the bank said: "In continuation to our filing with stock exchanges on February 14, 2018, we have to inform that quantum of reported unauthorised transactions can increase by $204.25 million."The Central Bureau of Investigation on Monday said it questioned PNB Executive Director K.V. Brahmaji Rao, two General Managers and a retired official in connection with its probe into the multi-crore fraud.The Income Tax Department also said it had attached 66 more bank accounts related to accused Choksi.Earlier, PNB, the second largest public sector bank in India, had said it had detected a $1.8 billion fraud in the Brady House Branch in Mumbai."The bank has detected some fraudulent and unauthorised transactions (messages) in one of its branches in Mumbai for the benefit of a few select account holders with their apparent connivance," the filing by PNB earlier said.Initially it had put the quantum of such transactions at around Rs 11,300 crore.The bank's shares dropped drastically on Tuesday after this regulatory filing and it was trading at Rs 102.45 per share, down 8.45 per cent at 10.46 a.m.