(CNN) -- Russian curler Aleksandr Krushelnitckii is suspected of failing a doping test at the PyeongChang Olympic Games.
Krushelnitckii, who won bronze in the mixed doubles event at this year's Olympics, is awaiting the results of a so-called "B sample," which could known as early as this evening local time in South Korea.
The Court of Arbitration for Sport (CAS) said in a statement Monday it has initiated the process of reviewing Krushelnitckii's case after a request by the International Olympic Committee (IOC). A hearing date has not been set, the statement said.
Earlier in the day, Konstantin Vybornov, a spokesman for the Olympic Athletes from Russia, declined to name Krushelnitckii but said an official comment would be made after the results of the second test.
More than 160 Russian athletes who could prove they were clean from doping are competing in a Olympic Athletes from Russia (OAR) team after the nation was banned from the Games because of state-sponsored doping leading up to and including the 2014 Sochi Winter Games.
Japanese speed skater Kei Saito was sent home from the Olympic village last week after becoming the first athlete at the 2018 Olympic Games to return a positive drugs test. The Court of Arbitration for Sport (CAS) said Saito voluntarily accepted his provisional suspension after an out-of-competition test turned up signs of a masking agent.
The International Olympic Committee (IOC) said in a statement posted to Twitter it "cannot communicate on individual cases while the procedure is still ongoing," because "doping testing and sanctioning at the Olympic Winter Games Pyeongchang 2018 is independent from the IOC."
IOC spokesman Mark Adams said at a daily press briefing Monday it would be "extremely disappointing for us if a case is proven."
"On the other hand, what it does show is we have a system which is effective and protects the rights of the clean athletes," he added.
Several media outlets in Russia are reporting the positive test is for meldonium, the same substance for which tennis star Maria Sharapova was banned.
The use of meldonium, which was added to the list of banned substances by the World Anti-Doping Agency from 2016, is widespread in Russia and eastern Europe, where it is often taken as a heart drug.
The news of a doping case in the OAR team could mean the athletes won't be able to march in their national uniform and with the Russian flag at the closing ceremony.
Although they competed under the OAR flag, the IOC had said beforehand the Russian athletes may have been able to march in their own national colors at the closing ceremony if they stuck to its strict code of conduct on neutrality.
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