well, in a "60 minutes" investigation, armen keteyian reports that the whistleblowers who first uncovered the cheating have found that four gold medals from the 2014 winter games were won by russians on steroids. >> reporter: when it came to doping in russia, nobody was more powerful than grigory rodchenkov. he ran its drug testing lab, and e d the ability to make positive drug tests disappear. the wada report called him the heart of russian doping. in the wake of the scandal, rodchenkov was fired by the kremlin and has since taken refuge in the u.s. for fear of his own safety because of how much he knows. over the last few months, shdchenkov has been sharing what pa knows with vitaly stepanov. that he doesn't know is that stepanov has recorded 15 hours of their conversations. what rodchenkov has revealed threatens the credibility of the results at the 2014 winter games in sochi, russia. >> he told me what i knew they did. we could-- we could only see this much, but what was happening with cover-ups, it's like this. >> reporter: rodchenkov, who ran the drug testing lab in sochi, bragged h

tonight armen keteyian has learned more about this russian operation. >> reporter: the international olympic committee said today it's considering retesting blood and urine samples from this now- erinted russian lab at the 2014 winter games in sochi. but based upon what we have learned from the lab's former director, any positive drug tests disappeared a long time ago. dr. grigory rodchenkov shared details of a systematic cover-up il sochi during skype conversations with vitaly stepanov, a former russian anti- doping official-turned key eyistle-blower. stepanov allowed us to listen the 15 hours of conversation he secretly recorded with rodchenkov. >> he had the ability to help to r:t the necessary results. me reporter: and those necessary results were gold medals? >> yes. >> reporter: in the recordings, rodchenkov named russian gold medalists in three sports, bobsled, skeleton and cross country skiing, whose dirty drug tests he helped cover up, all part, he said, of an elaborate scheme to protect russia's olympic medal winners with the help of the country's intelligence service known

tonight, armen keteyian has learned more about this russian operation. >> reporter: the internationalples from this now tainted russian lab at the 2014 winter games in sochi. but based upon what we've learned from the lab's former director, any positive drug tests disappeared a long time ago. dr. grigory rodchenkov shared details of a systematic cover-up in sochi during skype conversations with vitaly ep anti-doping official turned key whistleblower. stepanov allowed us to listen to 15 hours of conversations he secretly recorded with rodchenkov. >> he had the ability to help to get the necessary results. >> and those necessary results were gold medals? >> yes. >> reporter: in the recordings rodchenkov named russian gold medalists in three sports -- bobsled, skeleton and cross-country skiing, whose dirty drug tests he helped cover up, all part, he said, of an elaborate scheme to protect russia's olympic medal winners with the help of his country's intelligence service, known as the fsb. what did he tell you about the fsb? >> that fsb tried to control every single step of the anti-dopin