Russia's Olympic Committee has confirmed that a Russian athlete at the Pyeongchang Winter Games has tested positive for the banned substance meldonium.
Following a second test, the Russian delegation said "we express our sincere regret over the fact of the incident.'' But it said the test results indicate curler Alexander Krushelnitsky only consumed meldonium once.
It noted that it would be "useless" if the intent was to enhance performance.
Krushelnitsky won the bronze medal in Pyeongchang with his wife in mixed doubles curling.
Meldonium is a drug designed for people with heart problems and some believe it can help athletes increase stamina. It was banned in sports in 2016.
Russian tennis star Maria Sharapova was suspended for 15 months after testing positive for meldonium at the Australian Open in 2016.