The Court of Arbitration for Sport (CAS) has confirmed its anti-doping division has "initiated a procedure" involving Russian curler Aleksandr Krushelnitckii.
Krushelnitckii partnered wife Anastasia Bryzgalova to bronze in the mixed doubles at the Winter Olympics last week, beating Norway for a place on the podium.
Reports emerged on Sunday alleging that a member of the Olympic Athletes from Russia team (OAR) had failed a doping test, although the International Olympic Committee (IOC) refrained from identifying any competitor in a statement that stressed it would be "extremely disappointing" if a case is proven.
But CAS revealed on Monday that, in response to a request from the IOC, it has registered a new procedure involving Krushelnitckii.
No hearing date has been set and CAS said it would provide no more information on the case until further notice.
An earlier statement from OAR spokesperson Konstantin Vybornov read: "Due to the large amount of unreliable information that has appeared regularly in various media, especially foreign ones, over the last two days in connection with a positive doping test of one of the members of the Olympic Athletes from Russia, we would like to emphasise that the official position of our delegation lies in the fact that, before the results of the 'B' sample, we will not comment on the situation, nor will we name the athlete or the sport.
"Any other references to official statements or the words of representatives of our delegation are untrue. "Further comments from our side will only be made after the results of the opening of the 'B' doping test."