The former head of Russia's drug testing laboratory has told a whistleblower that at least four of Russia's gold medallists at the 2014 Winter Olympics were using steroids, according to a soon to be aired interview.
CBS News is reporting that Vitaly Stepanov, who previously worked for Russia's anti-doping agency, told investigative programme "60 Minutes" that Grigory Rodchenkov, the former head of the laboratory, has evidence of the use of banned substances at the Games in Sochi, Russia.
Vitaly Stepanov is now living in the United States.
Reuters was unable to independently confirm the disclosures in the "60 Minutes" report.
The World Anti-Doping Agency (WADA) said the body was aware that Sunday's programme would include content regarding further doping allegations.
"We will watch the programme with interest," WADA spokesman Ben Nichols told Reuters.
"We will not comment further until we have viewed the programme in full."
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.
WADA and the International Association of Athletics Federations have said its athletes will be allowed to return to competition when Russia can prove that it has met several conditions regarding its anti-doping operation.