Kamila Valieva's anti-doping sample showed traces of three drugs that can be used to treat heart conditions, according to a New York Times report.
The 15-year-old Russian figure skater is being allowed to compete at Beijing 2022 despite testing positive for banned angina drug trimetazidine.
The report said it also showed hyproxen and L-Carnitine, which are not banned.
The combination of substances prompted "a lot of red flags", United States anti-doping chief Travis Tygart said.
"Those are three substances that are all used for increasing performance," he told BBC sports editor Dan Roan on the Sports Desk Podcast, explaining they can increase endurance and reduce fatigue.
The case is ongoing and Valieva has the right to request the testing of her B sample, under World Anti-Doping Agency (Wada) rules.
She goes into Thursday's free skate top of the standings and on track for victory - but if she finished in the top three, there will be no medal or ceremony until her anti-doping case has been concluded.
The medals for the team event, where she helped the Russian Olympic Committee to victory before learning of the failed test, are also on hold for the same reason.
The International Olympic Committee (IOC) said on Tuesday that Valieva has argued her positive drugs test was due to contamination with her grandad's medicine.
Neither the IOC nor Russian Olympic Committee has commented on the report that the Stockholm laboratory that processed the sample had found evidence of three drugs.
In its report, the New York Times cited documents filed in Valieva's arbitration hearing this week and confirmed by someone who took part in the hearing.
Valieva was allowed to continue competing at the Games after the Court of Arbitration for Sport (Cas) ruled that a provisional suspension by the Russian Anti-Doping Agency should not be re-imposed on grounds of her age and the timing of the result, which came almost six weeks after she gave the sample.
Asked if it was a shame that the Valieva case had clouded the Games, Team GB's chef de mission Georgie Harland told BBC Sport: "Absolutely. It is very sad.
"For many of these athletes, this will be the only time they come to an Olympic Games. This is their experience. They have come here to compete and expect an outcome as part of that. It is highly likely we won't have that here."
'Catastrophic failure of anti-doping system'
Sports fans and clean athletes have been let down by a "catastrophic failure of the anti-doping system" in the Valieva case and the whole matter "just undermines the confidence of the system", Tygart said.
He said the IOC - which provides half the budget for Wada - needed to be separated from Wada to "let Wada actually do its job to ensure that clean athletes are the only ones competing and ultimately that's going to be beneficial for the Olympic movement".
He said it could now take the big sponsors and broadcasters to make a stand in order to force change.
"I think it's going to take ... those who are investing tens of millions of dollars into the Olympic movement to stand up and say, 'we're done with this unless you clean it up'," he said.
"'We are going to take our sponsorship dollar, our broadcast dollars and move it elsewhere to properties that are actually trying to protect the integrity of their competition.' I think we're getting close to that point."
He added that he did not think it was by coincidence that television viewing figures in the United States and other countries were at a low for these Games.
"It's historic lows - the lowest Winter Olympic viewership that NBC has had," he said. "It's unacceptable. We're in a time of Covid when a lot of people are stuck in their homes, it should be the highest quite frankly.
"At some point are those that are entrusted to protect the values and property value of the Olympic rings, are they going to wake up to the fact that people don't want to watch a a rigged competition, that enough is enough, let's get it cleaned up?"
IOC spokesman Mark Adams told a news conference on Wednesday that there would simply be an asterisk next to the results at the end of the women's and team competitions for now, adding: "We would prefer not to have that going on. My heart goes out to the athletes but the IOC has to follow the rules."
Valieva was emotional at the end of her short programme on Tuesday and Adams said her welfare was the priority for the IOC, which will not insist she attends the customary news conference if she finishes among the top three.
"She is in the centre of a lot of speculation. It must be very tough for her," Adams said. "We are of course in touch with the team. Her welfare is the team's first priority and obviously we are very careful of that."