(Reuters) - CBS News says the former head of Russia's drug testing laboratory Grigory Rodchenkov has told whistleblower Vitaly Stepanov that at least four of Russia's gold medal winners at the 2014 Winter Olympics were using steroids, according to an interview to be aired on Sunday. Stepanov, who previously worked for Russia's anti-doping agency and is now living in the United States, told the investigative program "60 Minutes" that Grigory Rodchenkov, the former head of the drug laboratory, had evidence of the use of banned substances at the Games in Sochi, Russia. The World Anti-Doping Agency (WADA) said the body was aware that Sunday's program would "include content regarding further doping allegations".
