The bank, however, could not find any past entries in the system, the FIR has alleged.
Billionaire jewellery designer Nirav Modi and other members of his family, who fled the country last month, allegedly made fraudulent transactions of over Rs 11,400 crore through 150 letters of understanding issued by the Punjab National Bank, officials said.
Nirav Modi, who holds an Indian passport, left India on January 1, while his brother Nishal, a Belgian citizen, also left the country on same day. However, whether they travelled together has to be probed, they said.
Nirav Modi's wife Ami, a US citizen, left on January 6 and his uncle and business partner Mehul Choksi, the promoter of Gitanjali jewellery chain, left on January 4, the officials said.
The bank became suspicious only on January 16 when the accused companies --Diamond R US, Solar Exports and Stellar Diamonds (all accused in the CBI FIR) -- approached it with import documents and a request to issue Letters of Understanding (LoUs) for raising buyers' credit for making payments to the overseas suppliers.
The bank, however, could not find any past entries in the system, the FIR has alleged.
It approached the CBI on January 29 with a complaint of Rs 280 crore fraud, officials said.
Nirav Modi, who is believed to be in Switzerland, was also present in a group photograph of Indian CEOs with Prime Minister Narendra Modi, issued by the Press Information Bureau, during the World Economic Forum on January 23, six days before the bank sent its first complaint against him to the CBI, according to the officials.
The agency immediately swung into action registering an FIR on January 31 followed by searches at 20 locations in Mumbai and Surat and issued a look out circular on February 4 against Nirav Modi and three absconding accused, they said.
A look out circular is issued by enforcement agencies to all exit and entry ports to inform them about the movement of an accused.
Nirav Modi, a regular on the lists of rich and famous Indians since 2013, was booked by the CBI, along with wife, brother and business partner Choksi on January 31, for allegedly cheating the state-run Punjab National Bank to the tune of Rs 280 crore.
The bank again approached the CBI within a fortnight of the first complaint giving details of more transactions which were over Rs 11,400 crore.
The question why the PNB did not send a complaint to the CBI and decided to give it in tranches is also under the scanner of the agency, they said.
An LoU is a letter of comfort issued by one bank to branches of other banks, based on which foreign branches offer credit to buyers.
The bank has claimed in three complaints to the CBI that so far it has detected 150 LoUs which were fraudulently issued by its officials in connivance with Nirav Modi and the other accused in the case, officials said.
The agency is analysing the fresh complaints and will take a call whether to register fresh FIRs or expand the ambit of the existing FIR related to fraudulent transactions of worth Rs 280 crore, they said.
In these cases, the bank has alleged that the LOUs were issued to Hong Kong based branches of Allahabad and Axis bank, they said.
The PNB has claimed in the complaint that overseas branch of banks used the funds to clear their own liabilities, the officials said.
During searches conducted by the agency which included the residences of Nirav Modi and the other accused along with companies, the CBI recovered 95 crucial documents related to import bills, they said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)