As tensions rose between Russia and the United States, Russian authorities detained Brittney Griner, a W.N.B.A. star, on drug charges. The Russian Federal Customs Service announced Ms. Griner’s detention on Saturday but said she was stopped at the Sheremetyevo airport near Moscow last month.

The detention of Ms. Griner, 31, a seven-time W.N.B.A. All-Star center for the Phoenix Mercury and a key figure in two champion Olympic teams, comes during an inflamed standoff between Russia and the United States over Russia’s invasion of Ukraine and pulls the player in the middle of the most acute crisis between the two countries since the Cold War.

Here is what we know so far about Ms. Griner’s detention.

Russia is talking about potentially serious charges.

The Russian Federal Customs Service said that a sniffer dog had prompted it to search the carry-on luggage of an American basketball player at the Sheremetyevo airport near Moscow, and that it had found vape cartridges containing hashish oil. A state-owned Russian news agency then identified the player as Ms. Griner.

Hashish oil is a marijuana concentrate that has a high concentration of the psychoactive chemical THC, and it is commonly sold in cartridges that are used in vape pens. The Russian Federal Customs Service said that customs officers had noticed vapes after scanning the traveler’s bag.

The customs service said that a criminal case had been opened into the large-scale transportation of drugs, a charge that could carry a sentence of up to 10 years in prison.

It released a video of a traveler who appeared to be Ms. Griner going through airport security with a trolley suitcase and a small backpack, followed by footage of someone examining a package that appeared to be from the traveler’s suitcase.

“Brittney has always handled herself with the utmost professionalism during her long tenure with USA Basketball,” U.S.A. Basketball said on Twitter.

The timing of the detention remains murky. Its political implications do, too.

The screening at the airport occurred in February, according to the Customs Service, raising the possibility that Ms. Griner had been in custody for at least several days. She last posted on Instagram on Feb. 5. The timing provided leaves open the possibility that the case could have been underway in secret for weeks before Russian authorities chose to draw attention to it.

It is still unclear whether Russia might have targeted Ms. Griner as leverage against the United States, which has led a widespread effort to impose harsh sanctions on Russia and its elite.

Citing privacy constraints, Secretary of State Antony J. Blinken did not comment on the detention on Sunday at a news conference in Chisinau, Moldova, and did not respond to a question about whether Russia had announced her arrest as retaliation for the economic, military and diplomatic pressure the United States has leveled against Russia in recent days.

But American officials have repeatedly accused Russia of detaining U.S. citizens on doubtful pretexts.

“This follows a pattern of Russia wrongly detaining & imprisoning US citizens,” Representative Joaquin Castro, Democrat of Texas, wrote on Twitter on Saturday, citing the case of Trevor Reed, a former U.S. Marine whom a Russian court sentenced to nine years in prison in 2020 on charges of violence against police officers that his family and supporters described as fraudulent.

On Saturday, the State Department released an updated advisory urging American citizens to leave Russia immediately given the “potential for harassment against U.S. citizens by Russian government security officials.”

Ms. Griner was in Russia to play. Many W.N.B.A. stars rely on income from overseas leagues.

Ms. Griner has played for the Russian team UMMC Ekaterinburg for several years during the W.N.B.A. off-season.

Many American players compete with high-paying Russian teams: about 70 W.N.B.A. players have decided to play with international teams instead of resting during the off-season this year, with more than a dozen in Russia and Ukraine.

A W.N.B.A. spokeswoman said on Saturday that all the others had already left Russia and Ukraine.

The financial incentives are compelling. W.N.B.A. players make a fraction of what their male counterparts do, with their maximum salary in 2022 at $228,094 while the top N.B.A. players are paid tens of millions of dollars.

International female teams, which tend to have more government and corporate financial support than those in the W.N.B.A., can pay hundreds of thousands of dollars a season, and sometimes more than $1 million.

Some observers criticized the gender pay gap in American basketball in connection to Ms. Griner’s detention.

The public statements are cautious, but supporters are rallying around Ms. Griner.

Mr. Blinken said the State Department would “provide every possible assistance” to any American held by a foreign government.

“Whenever an American is detained anywhere in the world, we of course stand ready to provide every possible assistance,” Mr. Blinken said. “And that includes in Russia.”

The W.N.B.A. said in a statement that Ms. Griner “has the W.N.B.A.’s full support and our main priority is her swift and safe return to the United States.”

The Mercury also released a statement saying that they “love and support Brittney” and that their main concern was her safety, her physical and mental health and her safe return home.

“Thank you to everyone who has reached out to me regarding my wife’s safe return from Russia,” Ms. Griner’s wife, Cherelle T. Griner, posted on Instagram on Saturday, adding, “We continue to work on getting my wife home safely.”

Lara Jakes contributed reporting from Chisinau, Moldova.