The World Anti-Doping Agency (WADA) is to investigate doping allegations levelled at unnamed Russian athletes in relation to the 2014 Winter Olympic Games in Sochi.
A CBS 60 Minutes report last Sunday claimed that four gold medallists were among the athletes to have taken banned substances at the Games in Russia.
Vitaly Stepanov blew the whistle on track and field athletes before Russia was banned by the IAAF last year and the former Russian anti-doping officer has now made further claims about drug use and cover-ups during the Games two years ago.
A WADA statement said: "The World Anti-Doping Agency [WADA] announces that it will immediately probe the new Russian doping allegations, related to the 2014 Sochi Olympic Games, which were broadcast on Sunday on CBS 60 Minutes.
"The broadcast features additional allegations of doping misconduct by Russian athletes and entourage members at the Sochi Games that had not previously been exposed.
"On the basis of recorded conversations between Vitaly Stepanov and the former Moscow Laboratory Director, Dr. Grigory Rodchenkov, the broadcast claims that numerous Russian athletes were doped at Sochi; including, four gold medallists that were using steroids.
"The broadcast also suggests that the Russian Federal Security Service [FSB] interfered with the Games anti-doping program; including, some FSB agents having been employed as Doping Control Officers [DCOs]. WADA has not yet been able to independently verify these allegations, but will now conduct further inquiries into the allegations without delay.
"This includes initiating the process to access the recorded conversations in which Dr. Rodchenkov aired his views, as cited in the program."
WADA president Craig Reedie said: "WADA will probe these new allegations immediately. The claims made in the program offer real cause for concern, as they contain new allegations regarding attempts to subvert the anti-doping process at the Sochi Games.
"Mr. Rodchenkov was of course interviewed by WADA's Independent Commission that exposed widespread doping in Russian athletics last year; yet, regrettably, he was not forthcoming with such information related to the Sochi Games.
"It is surprising to hear these views so many months after the Commission concluded its work.
"On behalf of WADA, I would also like to acknowledge that the Stepanovs who, as reflected by 60 Minutes and other media outlets, felt there was some level of inaction by WADA in the period leading up to the formation of our Independent Commission in January 2015.
"There is no question that the Stepanovs provided vital information and intelligence that allowed the Commission to be established; and, without which, widespread doping in Russian athletics may never have truly been exposed.
"What may have appeared as inaction reflected the fact that, until the revised World Anti-Doping Code came into effect on 1 January 2015, WADA did not have the power to conduct its own investigations.
"At the time, the Agency was only able to collect information and pass it on to those that did have the power to investigate, in this case, the Russian authorities. WADA believes that passing the whistleblowers' information on to the Russian authorities would not have resulted in the required scrutiny."