Kamila Valieva’s sample included three substances sometimes used to help the heart. Only one is banned.

“It’s a trifecta of substances — two of which are allowed, and one that is not allowed,” Travis Tygart, the chief executive of the United States Anti-Doping Agency, said when told of the discovery. He added that the benefits of such a combination “seem to be aimed at increasing endurance, reducing fatigue and promoting greater efficiency in using oxygen.”

Earlier on Tuesday, a member of the International Olympic Committee’s executive board told reporters that Valieva’s positive result might have stemmed from a case of contamination with medication that her grandfather had been taking. And in testimony provided to an earlier hearing with Russian antidoping officials on Feb. 9, and later submitted as evidence in Sunday’s hearing in Beijing, Valieva’s mother said her daughter had been taking Hypoxen because of heart “variations.”

Valieva’s grandfather did not testify in the original hearing in Russia, but he did provide a video shot in a car, according to a portion of the document. In the video, the document said, he said that he had used trimetazidine periodically when he experienced “attacks” and showed a packet of the medication to the camera. Valieva’s mother said in her evidence in the Russian hearing that Valieva’s grandfather had accompanied the teenager to practice on a daily basis and had stayed with Valieva until her mother returned home from work.

L-carnitine, a naturally occurring substance that converts fat into energy, has surfaced in significant doping cases in the past. In 2019, Alberto Salazar, then a coach of some of the world’s top distance runners, was barred from the sport for four years in part for giving improper infusions of the substance to his athletes in an effort to bolster their performance. Salazar’s ban has since been made permanent.

L-carnitine is allowed when taken orally, Tygart said, but prohibited if given in large amounts by an infusion or IV because it could give an unfair performance-enhancing advantage. It was not clear how Valieva had taken the supplement, or the concentration in her sample.