Russian figure skater Kamila Valieva has said she tested positive for doping due to a "contamination" from her grandfather's heart medication, a senior IOC member said Tuesday.

Valieva made the claim at a hearing at the Beijing Olympics.

"I was not in the hearing but her argument was this contamination which happened with a product her grandfather was taking." Denis Oswald told reporters after an IOC media briefing in Beijing.

Russian media said Valieva allegedly drank from the same glass that her grandfather, who has a heart condition, had used.

Valieva will skate in the Olympic women's singles competition later Tuesday after the Court of Arbitration for Sport ruled the 15-year-old could take part despite failing a drugs test.

She tested positive in December for trimetazidine, a drug used to treat angina but which is banned by the World Anti-Doping Agency (WADA) because it can increase blood flow efficiency and help endurance.

Oswald, a lawyer who oversaw the International Olympic Committee's sanctions stemming from mass Russian doping at the 2014 Sochi Games, said the substance was not one a girl of Valieva's age would take.

"It's true the product is a bit strange, especially for a girl of her age," he said.

"But again, as long as we don't know exactly how it happened, it's hard to make a judgment."

Russian bobsleigh athlete Nadezhda Sergeeva tested positive for trimetazidine during the 2018 Pyeongchang Winter Olympics, but CAS later canceled her suspension because it ruled the positive test was caused by a contaminated supplement.

American swimmer Madisyn Cox had her two-year ban cut to six months in September 2018 after proving that the trimetazidine found in her system had come from a tainted multivitamin supplement.

Oswald also said the entourage around Valieva – her coaches and advisors – would be investigated.

"It is a wish to examine all aspects of this case, including the entourage of the girl," he said at the media briefing.

"Of course you can imagine a girl of 15 does not do something wrong alone.

"The entourage will be investigated."