Concerned over a massive Rs 11,000-crore fraud at PNB remaining undetected for years, markets regulator Sebi may give a fresh push to its "on-hold" proposal to mandate listed firms to disclose all loan defaults within a day. While billionaire jewellery designer Nirav Modi, the alleged perpetrator of this fraud, is not directly linked to any listed company, his relative and business associate Mehul Choksi's Gitanjali Gems is a listed firm and has been involved in some other cases of suspected market manipulations. Sebi has already launched a probe into trading and disclosure related issues in the matter of Punjab National Bank (PNB) and Gitanjali Gems in connection with the biggest fraud in the Indian banking industry so far, allegedly perpetrated by absconding Modi.