Investigating agencies are digging deeper into the alleged Rs 11,400-crore Punjab National Bank (PNB) fraud. The Enforcement Directorate (ED) has now summoned PNB officials and directors of subsidiaries linked to diamantaires Nirav Modi and the Gitanjali Group, owned by Mehul Choksi.

The Central Bureau of Investigation, on the other hand, is questioning Gokulnath Shetty, the former deputy manager at PNB's Brady House branch, who is believed to be the mastermind behind the alleged Rs 11,400-crore fraud.

During questioning, Shetty told investigators how he gamed the SWIFT financial messaging system to help Nirav Modi and his associates carry out the alleged fraudulent transactions.

Meanwhile, the ED has shortlisted movable and immovable properties of Nirav Modi and Mehul Choksi and the attachment process is likely to begin soon. ED suspects that the entire Rs 11,400 crore (the alleged fraud amount) has gone out of India.

The searches at properties of Nirav Modi and Mehul Choksi are still on. Last week, ED seized diamonds and jewels worth more than Rs 5,000 crore during searches at various properties and showrooms of Nirav Modi across India.

Top officials of the Punjab National Bank are also meeting the Central Vigilance Commissioner today, a day after being summoned by the agency in the wake of the alleged Rs 11,400-crore fraud.

PNB's BRADY HOUSE BRANCH SEALED

In another development, the Central Bureau of Investigation (CBI) today sealed PNB's Brady House branch, where the alleged Rs 11,400-crore fraud took place.

A notice on the sealing of the PNB branch in Mumbai has been put up outside the premises. Entry and exit of PNB officials at this branch have been prohibited till further orders from the CBI.

Following the CBI notice, PNB's Brady House branch will not deal with any banking operations.

The Brady House branch of PNB is a corporate branch which has high networth individuals and businessmen as its clients. This PNB branch in south Mumbai is not meant for retail bank customers.

FORMER PNB EMPLOYEE QUIZZED

CBI has seized service records and files of Gokulnath Shetty, the former deputy manager at PNB's Brady House branch, who is believed to be the mastermind behind the alleged Rs 11,400-crore fraud.

CBI is looking into the possible role of senior PNB officials who ensured that Shetty is not transferred from the branch.

During questioning, Shetty revealed that he would first send SWIFT messages of small amounts, which were uploaded on the bank's system so that no one would suspect any wrongdoing.

Later, these messages were modified and bigger financial transactions were carried out. The modifications made in the SWIFT messages were not updated on the bank's system. This is one of the reasons why the alleged fraud at PNB went undetected for such a long time.

WATCH: CBI summons Nirav Modi's chief financial officer Vipul Ambani, grills him for 8 hours</p>