The CBI on Thursday said it is examining two officials of overseas branches of an Indian bank in connection with its ongoing probe into the Rs 13,500 crore Punjab National Bank (PNB) fraud case involving diamond jeweller Nirav Modi and his uncle Mehul Choksi of the Gitanjali Group.

Two Deputy General Manager (DGM)-rank officials of the State Bank of India (SBI)’s Frankfurt and Mauritius branches were asked to join the investigation at its Mumbai’s Bandra office.

According to Central Bureau of Investigation (CBI) officials, the bank had issued buyer’s credit to exporters of Nirav Modi and Choksi firms on the basis of Letters of Undertakings (LoUs).

On Wednesday, the CBI had examined two officials of Canara Bank’s Bahrain Branch and one from Bank of India’s Antwerp (Belgium) Branch over the role of these branches in extending credit facilities on the basis of LoUs issued by the PNB to the firms related to Modi and Choksi.

The CBI on Sunday also questioned an officer who dealt with forex transactions in Allahabad Bank’s Hong Kong Branch.

The agency’s move comes days after a special CBI court here on Sunday issued non-bailable warrants against Modi and Choksi as both diamond traders, who left India in January, refused to join the investigation into the scam.

Modi, a regular on the lists of rich and famous Indians since 2013, along with his group companies — Diamond R US, Stellar Diamond and Solar Exports, uncle and business partner Choksi and others — has been named in the mega scam, admitted by the PNB in February that led to a massive upheaval in the country’s banking system.

Earlier, a lookout notice was issued by the CBI against Modi and Choksi but they and their associates had fled the country. While Modi and his brother Nishal left India on January 1, his wife Ami, a US citizen, and Choksi left on January 6, all before the CBI received a complaint from the PNB on January 29.

The PNB has claimed in different complaints to the CBI that several LoUs — issued by one bank to other banks, based on which foreign branches offer credit to buyers — were fraudulently issued by its officials in connivance with Modi and other accused in the case causing huge losses to the bank.