Two Russian athletes have confirmed the existence of a doping cocktail described by Grigory Rodchenkov, the former head of a Moscow anti-doping lab, in the first admission of involvement since Russia was accused of running a state-sponsored doping program.

Rodchenkov fled to the U.S. after telling The New York Times newspaper that he had provided athletes with banned substances — including during the 2014 Sochi Olympics, which Russia hosted.

A probe by the World Anti-Doping Agency (WADA) accused Russia of running a state-sponsored doping program.

WADA is meeting next week to review a ruling imposing sanctions on Russian athletes. The International Olympic Committee is also expected to decide the fates of two dozen Russian athletes in December, ahead of the 2018 PyeongChang Olympics.

During the Sochi Olympics, Rodchenkov said, he provided Russian athletes with a doping cocktail of different steroids mixed with alcohol.

In Russia Rodchenkov's account has largely been dismissed as the product of fantasy and investigators have opened a case against him. Earlier this week, Russia issued a request for his extradition.

Two anonymous Russian athletes and an athletics manager interviewed by Russia’s biggest sports channel Match TV said on Wednesday the cocktail was given in the form of three unmarked pill containers with colored caps.