Kolkata: Tightening its grip in the multi-crore Saradha chit fund scam, the CBI on Saturday began grilling Assam based singer and filmmaker Sadananda Gogoi at its Salt Lake office on his link with jailed Sudipta Sen. Sources close to CBI officials investigating the Rs 20,000-crore chitfund scandal that affected millions of poor investors, said the investigating agency may summon Trinamool Congress Rajya Sabha member and Bollywood star Mithun Chakraborty. Official sources said a CBI team is likely to proceed to Mumbai and question Mithun Charkraborty next week. Earlier, the sleuths of the ED grilled the matinee idol in Mumbai. Chakraborty was Saradha Group Brand ambassador. (UNI)