New Delhi, Feb 28: The Central Bureau of Investigation (CBI) on Wednesday arrested an internal chief auditor of the Punjab National Bank in connection with the probe of the alleged Rs 12,636 crore fraud, allegedly committed by companies of diamond merchants Nirav Modi and Mehul Choksi. Also Read - Mumbai's Arthur Road Jail Awaits Nirav Modi, Keeps Special Cell Barrack Number 12 Ready

The internal auditor is identified as MK Sharma. He was reportedly responsible for auditing the systems and practices of Punjab National Bank’s Brady House Branch, from where fraudulent Letters of Undertaking (LoU) were issued to firms promoted by Modi and Choksi. Also Read - PNB Scam Case: After Nirav Modi Loses Legal Fight, India Says Will Liaise With UK For His Early Extradition | Key Points

Meanwhile, CBI wrote a mail to Nirav Modi, asking him to come back to India and join investigation. Nirav Modi replied that he had a business abroad and hence, he can’t join the investigation. Also Read - Nirav Modi To Be Extradited To India As UK Judge Accepts India's Prison Safety Assurance | Highlights

On Tuesday, Nirav Modi and Mehul Choksi had said that they can’t join the investigation as their passport had been revoked. The CBI said on Wednesday that Modi must contact the high commission of the concerned country and the agency would arrange his travel to the country.

Nirav Modi and Mehul Choksi on Tuesday responded to the Enforcement Directorate summons, saying they will not be able to return to India as their passports have been revoked. The agency is now set to move the court to secure non-bailable warrants against Choksi and Modi.

Modi and Choksi are accused of obtaining fraudulent letters of undertaking from the Punjab National Bank (PNB). A retired PNB deputy manager was arrested to facilitate the fraud.

Nirav Modi’s jewellery business Firestar Diamond on Monday filed for bankruptcy in the United States. The total wealth of the company is estimated to be  between$50 million to $100 million.