The New York Times reported Sunday that the athlete has been identified as Russian curler Aleksandr Krushelnitckii, who won a bronze medal with his wife, Anastasia Bryzgalova, in mixed doubles curling. The Times reports that traces of meldonium, a banned substance that increases blood flow, were found in Krushelnitckii's urine sample.

Two Russian state news agencies cited Konstantin Vybornov, spokesman for the Olympic Athletes from Russia team, as saying that the delegation received an official notification of the positive test from the International Olympic Committee.

The IOC said later Sunday that it had taken note of Vybornov's statement.

Vybornov said a "B" sample taken from the athlete will be analyzed within 24 hours but did not name the athlete or the sport involved.

A confirmed doping case could be an obstacle to Russia's efforts to have the Russian team formally reinstated in time for the closing ceremony.

"Doping testing and sanctioning at the Pyeongchang 2018 is independent from the IOC. Therefore, the IOC cannot communicate on individual cases while the procedure is still ongoing," the IOC said in a statement. "However, we take note of the statement by a spokesperson of the Olympic Athlete from Russia (OAR) delegation."

The IOC added that "if the case is confirmed, it will be considered" by the IOC body, which will be considering whether to reinstate Russia.

The Court of Arbitration for Sport, which rules on Olympic doping cases, said it had not received any notification.

"No new case received, and no rumors of it so far," Matthieu Reeb, the court's secretary general, said in an email.

According to statistics recently published by RUSADA, the Russian Anti-Doping Agency, Krushelnitckii and Bryzgalovoy were tested only once apiece in 2017. That number does not include tests that might have been done by the World Curling Federation, which does not release testing data, or a multinational pre-Games testing task force.

The Russian delegation and World Curling declined to comment when reached by ESPN.

Doping cases in curling are rare but not unheard of. There were no positive tests -- officially known as adverse analytical results -- out of 224 samples processed by WADA-accredited laboratories in 2016, according to WADA's testing report from that year, the most recent available. There were three positives in the Paralympic sport of wheelchair curling in 2016, including one case involving a U.S. athlete with cerebral palsy who did not request a proper therapeutic use exemption for a prescription medication and received a public warning rather than a suspension.

Canadian and Swedish athletes in wheelchair curling have previously been suspended for doping violations.

As part of IOC sanctions for Russian doping at the 2014 Olympics in Sochi, athletes from the country had to undergo IOC vetting including an examination of their drug-testing history before they were invited to the Pyeongchang Olympics. Dozens were rejected.

The IOC announced its suspension of the Russian Olympic Committee in early December and created a vetting process to decide which athletes, support staff and officials to "invite" to compete in Pyeongchang. Included in that announcement was a proviso that the suspension could be lifted by the start of the closing ceremony, provided that the delegation abided by rules of conduct.

All members of the "Olympic Athlete from Russia" team were required to sign an "integrity declaration" promising to adhere to anti-doping rules that apply to all athletes -- an extra layer of paperwork imposed because the IOC was the entity that invited them, as opposed to their national Olympic committee. The IOC also wrote conduct guidelines concerning apparel and use and display of the Russian flag, which athletes were permitted to have in their rooms at the Olympic village but not elsewhere. Russian fans, however, have not been stopped from displaying the flag and colors.

Nicole Hoevertsz of Aruba, chairwoman of the IOC panel that developed those guidelines, said at the Feb. 6 full IOC session that criteria for lifting the suspension was "a little bit open and flexible,'' and "individual incidents" will not necessarily result in the suspension being continued. The IOC leadership has never explicitly stated whether one or multiple doping violations would factor into the decision.

The only other doping case so far at the Pyeongchang Olympics came when Japanese short-track speedskater Kai Saito tested positive for a banned diuretic and was removed from competition. His case is ongoing.