New Delhi/Mumbai: The Central Bureau of Investigation (CBI) has arrested an internal chief auditor of Punjab National Bank (PNB) in its ongoing probe into Rs 12,600 crore bank fraud case.

"CBI has on Wednesday arrested an Internal Chief Auditor of Punjab National Bank in an ongoing investigation of the cases related to Nirav Modi group and Gitanjali group," a CBI official said.

The official also said that the arrested auditor has been identified as MK Sharma, Chief Manager rank of PNB.

According to the CBI official, Sharma was allegedly responsible for auditing the systems and practices of PNB, Brady House Branch in Mumbai and report the deficiencies to Zonal Audit Office.

The CBI official also said that Sharma would be produced in a court in Mumbai on Thursday.

Diamond trader Modi and owner of Gitanjali Gems, Mehul Choksi have been accused of defrauding the PNB of Rs 12,600 crore, with Rs 1,300 being added to the fraud kitty on Monday night.

Earlier, the amount stood at Rs 11,300 crore.

The CBI had filed the first FIR in the scam on February 14 against Nirav Modi, his wife Ami, brother Nishal, uncle Choksi and his firms Diamond R US, Solar Exports and Stellar Diamond.

The agency stated that the fraud involved an amount of around Rs 6,400 crore.

Modi, his family and Choksi left the country in early January.

The CBI filed a second FIR on February 15 for Rs 4,886.72 crore fraud against Choksi's Gitanjali Group.

To date, 12 persons have been arrested by the CBI in connection with the case. The Enforcement Directorate has claimed to have attached properties worth Rs 6,000 crore.