Russia's sports ministry said on Monday it was 'certain' about the transparency of its doping controls during the 2014 Winter Olympics in Sochi, and that independent observers had managed the testing operation daily. The ministry was responding to allegations of a testing cover-up at the Sochi Games that included the use of intelligence agents from the country's Federal Security Service, known as the FSB. 'We are... certain about the transparency of doping controls during the Olympic Games,' the ministry said in a statement. 'In addition to Russian specialists, doping control stations also employed foreign experts. 'Furthermore, a team of independent observers managed the doping control operations on a daily basis during the Games.' Whistleblower Vitaly Stepanov told CBS News in an interview aired on Sunday that the former head of Russia's drug testing laboratory, Grigory Rodchenkov, had informed him he had evidence of a testing cover-up during more than 15 hours of taped conversations. Rodchenkov also said that at least four Russian gold medallists in 2014 were using steroids, CBS News investigative programme '60 Minutes' reported. Reuters was unable to independently confirm the disclosures in the '60 Minutes' report. Neither Rodchenkov nor Stepanov were immediately available for comment on Sunday. Stepanov told '60 Minutes' that Rodchenkov had told him 'FSB agents worked as doping control officers during the Sochi Games, that FSB tried to control every single step of the anti-doping process in Sochi'. FULL INVESTIGATION Stepanov previously worked for Russia's anti-doping agency (RUSADA) and is now living in the United States. 'Since the revelations by Stepanov originally appeared in 2015, a full investigation has been carried out into activities by the Russian state, RUSADA and all relevant parties,' the ministry said in its statement. 'Subsequently, we agreed a 'road map' with WADA (the World Anti-Doping Agency) to reform the anti-doping process so that the tests are being carried out by UKAD (UK Anti-Doping), using samples gathered by foreign companies, and analysing all tests in accredited labs. 'These efforts thus ensure the independence and transparency of doping control in Russia, which is fully supported by the state.' Russia is banned from all track and field competitions, including the Rio Olympics in August, after an independent WADA commission last November revealed widespread state-sponsored doping. UKAD is ensuring that targeted and intelligence-led testing is being carried out on Russian athletes inside and outside the country. Russian athletes will be allowed to return to competition when the country can prove it has met several conditions regarding its anti-doping operation, WADA and the International Association of Athletics Federations (IAAF) have said. WADA spokesman Ben Nichols told Reuters on Sunday that the allegations about Russian intelligence involvement in a doping cover-up, and that four Sochi gold medallists were doping, were 'very disturbing' and that his organisation would look into them.