The Central Bureau of Investigation, probing the ₹11,500 crore fraud in the Punjab National Bank, arrested a general manager with the bank late on Tuesday night.

CBI sources said Rajesh Jindal, General Manager, Credit, at the PNB head office in New Delhi, was arrested after inquiries established his culpability. Mr. Jindal was head of the Brady House branch of the PNB in Mumbai from August 2009 to May 2011. “It was during his tenure that the issuance of Letters of Undertaking (LoUs) to firms owned by the Nirav Modi group first started,” a senior CBI officer said.

Earlier on Tuesday, the CBI arrested three top officials of the Nirav Modi group, including Vipul Ambani — a nephew of founder of Reliance Industries, Dhirubhai Ambani.

Two senior employees in the firm of Mehul Choksi, Mr. Modi’s uncle, were also arrested.

Mr. Jindal, was bought to Mumbai on Wednesday and produced in a special CBI court along with Mr. Ambani and four others arrested in Mumbai on Tuesday — Kavita Mankikar, Arjun Patil, Kapil Khandelwal and Niten Shahi.

The CBI, in its remand application, submitted that all the six, who were questioned separately, have not been able to provide satisfactory explanations as to why they did not alert the relevant authorities about the misconduct relating to issuance of LoUs despite knowing of it. The agency said that in order to unearth the larger conspiracy and to identify others accused in the fraud, custodial interrogation of all the accused was required. A special CBI Judge remanded all six to CBI custody till March 5.