WNBA side Phoenix Mercury say they are concerned for Brittney Griner's "safety, physical and mental health" after the centre was detained in Russia on charges of drug smuggling.
The Olympic gold medal-winning American was reportedly taken into custody at a Moscow airport in February after cannabis oil was found in her luggage.
She could face a sentence of up to 10 years in a Russian prison if convicted.
Phoenix say they are "aware of and are closely monitoring the situation".
A statement from the WNBA club was posted on Twitter after the Russia Federal Customs Service said that an American basketball player was taken into custody after officials found vape cartridges that contained hashish oil in carry-on luggage at Sheremetyevo Airport.
Russian news agency TASS, citing a law enforcement source, has since identified the player as 31-year-old Griner, who has played in the country during the WNBA offseason since 2015.
"We remain in constant contact with her family, her representation, the WNBA and NBA," the club 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."
USA basketball has said that it is "monitoring the legal situation facing" Griner.
"Brittney has always handled herself with the utmost professionalism during her long tenure with USA Basketball and her safety and wellbeing are our primary concerns," the governing body said.