Stepanov, who previously worked for Russia's anti-doping agency and is now living in the United States, told investigative program "60 Minutes" that Grigory Rodchenkov informed him in over 15 hours of taped conversations he had evidence of a Sochi Games testing cover-up, which included the use of Russian intelligence agents.
Reuters was unable to independently confirm the disclosures in the "60 Minutes" report.
In an interview aired on Sunday, Stepanov said Rodchenkov told him "that FSB agents worked as doping controls officers during the Sochi Games, that FSB tried to control every single step of the anti-doping process in Sochi."
FSB refers to Russia's Federal Security Service.
CBS said it had listened to all 15 hours of tape and that at one point, Rodchenkov told Stepanov he was in possession of what he called "the Sochi list" of four Russian gold medal winners who were doping.
Neither Rodchenkov nor Stepanov were immediately available for comment.
World Anti-Doping Agency (WADA) spokesman Ben Nichols said the allegations about use of Russian intelligence in a doping cover-up and that four gold Sochi gold medallists were doping were "very disturbing".
"WADA has watched the CBS 60 Minutes program, which revealed new and very disturbing allegations regarding Russian doping in sport. We will look into these without delay," Nichols told Reuters in an e-mail.
Russia is already banned from all track and field competitions, including August's Rio Olympics, after an independent WADA commission last November revealed widespread state-sponsored doping.
Its athletes will be allowed to return to competition when Russia can prove that it has met several conditions regarding its anti-doping operation, WADA and the International Association of Athletics Federations have said.
