The questioning came a day after the CBI arrested four people - two employees and an auditor of Nirav Modi's group of companies, and a director of Gitanjali Group of Companies.
"PNB General Manager (Treasury) S K Chand is being questioned by the CBI in the bank fraud case," an agency official said.
It is alleged that Choksi and Modi got Letters of Undertakings (LoUs) and Foreign Letters of Credit (FLCs) of Rs 12,636 crore issued in favour of foreign branches of Indian banks based on fraudulent claims.
The accused officials of PNB did not enter the instructions for these LoUs and in their internal software to avoid scrutiny.
They were sent through an international messaging system for banking called SWIFT, which is used to pass instructions among banks globally to transfer funds.
An LoU is a guarantee which is given by an issuing bank to Indian banks having branches abroad to grant short-term credit to the applicant.
The PNB officials allegedly sent these messages to Indian banks - Canara Bank, State Bank of India, Bank of India, Axis Bank, Allahabad Bank - located in Antwerp, Hong Kong, Bahrain, Mauritius, Frankfurt without making entries in the banking software about the LoUs.
Upon receiving the messages from PNB under SWIFT, the banks abroad transferred these amounts into Nostro account of PNB with them.
Nostro account is an account that a bank holds in a foreign currency in another bank to enable foreign trade by its clients.