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US basketball authorities said on Saturday that an American star basketball player being held in Moscow on narcotics charges is two-time Olympic champion Brittney Griner.
The arrest came as tensions between Moscow and the West soar over Russia's invasion of Ukraine.
The Russian Federal Customs Service said that an inspection of hand luggage carried by a US citizen who arrived on a flight from New York in February "confirmed the presence of 'vapes' (and) a liquid with a specific smell".
It said an expert had determined that the liquid was the narcotic cannabis oil (hash oil).
The statement did not identify the jailed woman but said she was "a member of the US National Basketball Association, a two-time Olympic basketball champion in the US team".
The customs service said the detained woman faces a potential jail term of five to 10 years.
US basketball authorities announced that the woman was all-star Griner.
USA Basketball, the sport's governing body in the US, said on Twitter that it was "aware of and closely monitoring the legal situation facing Brittney Griner in Russia".
"Brittney has always handled herself with the utmost professionalism during her long tenure with USA Basketball and her safety and well-being are our primary concerns."
Griner, who is 31, is a seven-time all-star centre for the Phoenix Mercury of the Women's National Basketball Association (WNBA).
The team issued a statement echoing the language of USA Basketball in which they said, "We love and support Brittney, and at this time our main concern is her safety, physical and mental health, and her safe return home."
Griner, who is 2.06 metres tall, is the only woman in US college history to score 2,000 points and block 500 shots.
Many WNBA athletes spend the American off-season playing in European leagues, including the Russian and Ukrainian leagues.