NEW DELHI: The Central Bureau of Investigation on Monday sent an extradition request for Nirav Modi ’s younger brother Neeshal Modi in Rs 13,578 crore Punjab National Bank scam.Official sources said that the extradition request has been sent to ministry of home affairs, which will forward it to ministry of external affairs and then it will be formally handed over to the Belgian authorities.Neeshal, a Belgian national, is said to be living in Antwerp , from where he used to handle the diamond business of the family and where a large amount of funds is said to have been laundered by the brothers.An Interpol red corner notice had already been issued earlier against Neeshal, restricting his travel to different countries.Sources said that authorities are trying to bring back both Nirav and Neeshal Modi along with Mehul Choksi and top absconding executives of their companies for facing a trial here in India.Officials added that India has an extradition treaty with Belgium so getting him shouldn’t be a problem. “Once the extradition documents reach Belgium, the authorities there would be liable to trace and arrest him,” said a CBI officer.It is alleged that Neeshal Modi was "actively" involved in the scam, they said.He is alleged to be the beneficiary of funds siphoned off, instrumental in introducing dummy partners and changing pattern of partnership structure of companies, they said.He is also said to have formed several shell companies to support his brother’s illegal activities.Thirty-four-year-old Neeshal Modi, along with his brother Nirav Modi and uncle Mehul Choksi, fled the country in the first week of January this year, weeks before the scam surfaced in Brady House branch of Punjab National Bank in Mumbai.While Nirav Modi has been in the United Kingdom, Choksi is in Antigua and Barbuda where he has taken a citizenship.Replying to several e-summons sent by CBI and ED, both Nirav and Neeshal Modi have refused to come back to India and cooperate with the investigators.CBI has already filed chargesheet against the accused persons alleging that they got issued fraudulent Letters of Undertaking of more than $2 billion through Punjab National Bank's Brady House branch between during 2011 and 2017.An LoU is a guarantee given by an issuing bank to Indian banks with branches abroad to grant short-term credit to the applicant.Nirav Modi and his companies allegedly availed credit from the overseas branches of Indian banks using the fraudulent PNB guarantees given through LoUs and letters of credit issued by the Brady House branch which were not repaid, bringing the liability on the state-run bank, the officials said.