Olympic medallist Anna Chicherova has vowed to clear her name after learning she is one of 14 Russian athletes to have failed a doping retest.
The high jumper won bronze in 2008 but that result is now in doubt after 454 samples from those Games were retested.
"It's the most complete shock," said Chicherova, who went on to win gold at the 2012 Games in London.
"I can't explain how it could have happened. I was always sure what supplements and medicines I was using."
Earlier this month, the International Olympic Committee said up to 31 athletes from around the world could be banned from the Rio Olympics as a result of the retests, which were conducted using the latest scientific methods.
The Russian Olympic Committee subsequently revealed that 14 of those 31 athletes were Russian.
A Russian TV report then claimed those 14 athletes included 10 medallists, among them 33-year-old Chicherova, who is planning to defend her Olympic title at the Rio Games, which begin on 5 August.
Sports minister Vitaly Mutko admitted the news did not "look good" but said the results were "not an objective picture" of Russia's doping situation.
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