The Central Bureau of Investigation on Wednesday interrogated Narada News portal CEO Mathew Samuel in connection with a sting operation he claimed to have carried out five years ago, agency sources said. In the tapes that surfaced in 2016, ahead of the Bengal Assembly polls, persons resembling senior Trinamool Congress leaders and an IPS officer are seen accepting money from representatives of a fictitious company in return for favours.Mr. Samuel, who had been questioned by the agency on earlier occasions, too, appeared before the CBI on Monday afternoon at its Nizam Palace office, sources said. The CBI made its first arrest in the case last month when it apprehended IPS officer S.M.H. Mirza, who is currently in judicial custody. Prominent TMC leaders and Ministers, including Subrata Mukherjee, Subhendu Adhikary and Sougata Roy, and senior BJP leader Mukul Roy, who quit the Mamata Banerjee-led party two years ago, have also been quizzed by the probe agency over the past few weeks in the case.