SOCHI, Russia -- A Ukrainian cross-country skier has failed a doping test, her country's Olympic committee said Saturday. It is the third positive result of the Sochi Games.

Marina Lisogor tested positive for trimetazidine, which is classified as a “specified stimulant” on the World Anti-Doping Agency's prohibited list. Specified substances are considered more susceptible to inadvertent use and can carry reduced penalties.

The 30-year-old Lisogor competed in two cross-country events in Sochi, finishing far out of the medals.

According to the Ukrainian Olympic Committee, Lisogor said she did not knowingly take a banned substance.

Lisogor's failed drug test follows those of German biathlete Evi Sachenbacher-Stehle and Italian bobsledder William Frullani.

All three drug-test failures are tied to stimulants. The IOC is conducting 2,453 drug tests in Sochi, a record for the Winter Games. The Olympic body also stores Olympic doping samples for 10 years to allow for retesting when new methods become available.

Sachenbacher-Stehle, a former two-time Olympic gold medalist, tested positive for methylhexanamine in both samples. The German Olympic Committee said she was being sent home. She blamed a nutritional supplement and said she had never knowingly taken performance-enhancing drugs.

“I am going through the worst nightmare that you can imagine because I am unable to explain at all how there could be a positive test,” she said Friday.

Frullani was ejected from the games after testing positive for dimetylpentylamine. Frullani, who had not competed yet, asked for a backup test that confirmed the result.

The Italian Olympic Committee told the Associated Press it believed Frullani, a former decathlete, bought the stimulant on the Internet from the United States since it is not available in Italy.

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