- Auditor MK Sharma of PNB's Brady House branch in Mumbai arrested
- Mr Sharma will be produced in a Mumbai court tomorrow
- This Mumbai PNB branch is at the heart of Rs 11,400 crore scam
The CBI, however, has yet to track down billionaire jeweller Nirav Modi and his uncle Mehul Choksi, whose firms are accused of securing unauthorised loans using fraudulent letters of undertaking from India's second-biggest state lender.
Mr Modi and Mr Choksi left India in January before the fraud came to light. They have said in letters and statements that they are innocent.
CBI said the arrested auditor, MK Sharma, was "allegedly responsible for auditing the systems and practices" of Punjab National Bank's (PNB) Brady House branch in Mumbai and for reporting any problems to the zonal audit office.
Mr Sharma will appear in a Mumbai court on Thursday, the spokesman added. Mr Sharma could not immediately be reached for comment.
The agency earlier on Wednesday said that they have sent an email to Mr Modi asking him to join the investigation by next week. It has already stepped up questioning of various present and past officials of PNB.
So far it has arrested at least 13 people - seven from the bank and six more from Mr Modi and Mr Choksi's companies. Investigators have also seized a number of properties from the two, including jewellery and luxury vehicles.
Mr Modi and Mr Choksi, owner of Gitanjali Gems Ltd, are suspected of colluding with bank officials at PNB to obtain unauthorised loans over a six-year period starting in 2011.
The scale of the fraud has raised concerns about the potential for similar cases across India's banking sector. The Finance Ministry on Tuesday set a 15-day deadline for state banks to take action to improve their oversight of operational and technological risks.