The Russian delegation to the Pyeongchang Winter Olympics says a second sample from curler Aleksandr Krushelnitsky, who won a bronze medal, has tested positive for the banned substance meldonium.
"We express our sincere regret over the fact of the incident," the delegation says in a February 20 statement. But it also said results indicated Krushelnitsky only consumed meldonium once.
The Russian statement says that would be "absolutely useless and ineffective" if the intent was to enhance performance. It has not provided any data from the test.
The second sample was from the same day as the first one. The samples are split into two bottles and tested separately to ensure that lab-equipment error doesn't result in a false positive.
The Russian Olympic Committee has set up its own investigation, which could treat the issue as a criminal matter.
Russian curling officials have previously suggested that Krushelnitsky could have been set up by a rival Russian athlete or Russia's political enemies.
He and his wife, Anastasia Bryzgalova, won bronze in mixed-doubles curling.
Meldonium, which was banned in sports in 2016, is the same substance that led to Russian tennis star Maria Sharapova being banned from WTA competition for 18 months.
The drug is designed for people with heart problems and some believe it can help athletes increase stamina.
Also on February 20, Slovenian hockey player Ziga Jeglic became the third athlete to be caught doping at the Pyeongchang games, besides Krushelnicky and Japanese short-track speedskater Kei Saito, who failed a precompetition test.
The Court of Arbitration for Sport said Jeglic tested positive for fenoterol in an in-competition test. Fenoterol is a drug designed to open the airways to the lungs. Jeglic said it was an asthma drug that he took under doctor's orders.