State-run Punjab National Bank today said it had detected "some fraudulent and unauthorised" transactions amounting to around Rs 11,360 crore at a branch in Mumbai.

Soon after news of the fraud detection broke, sources from within the Central Bureau of Investigation said the agency had begun probing billionaire jeweller and diamond trader Nirav Modi in connection with today's fraudulent transactions.

The CBI began investigating after receiving two complaints from the Punjab National Bank over the fraudulent transactions, sources said. The agency is yet to file a First Information Report (FIR) in the matter.

Modi had previously come under the CBI's radar after the agency launched an investigation into accusations that he and others defrauded PNB of Rs 280 crore.

Earlier, PNB said the fraudulent transactions were for the "benefit of [a] few select account holders with their apparent connivance". Based on the fraudulent transactions, "other banks appear to have advanced money to these customers abroad", Punjab National Bank added.

"In the bank these transactions are contingent in nature and liability arising out of these on the bank shall be decided based on the law and genuineness of underlying transactions," PNB also said.

PNB, the country's second-biggest state-run lender and fourth-biggest overall by assets, did not name the people involved in its statement but said it had reported the deals to law enforcement agencies and would evaluate later whether it faces any liability arising out of the transactions.

The bank's stock took a hit after it announced the detection the fraud. PNB shares were trading 9.6 per cent lower than yesterday's closing at 3.15 pm on the Bombay Stock Exchange.

Input feeds : Syndicate Agency