Peng Shuai is at the centre of growing concern after the tennis star alleged earlier this month that a powerful Chinese politician sexually assaulted her.
The 35-year-old Peng, a former world number one in doubles, has not been seen since.
It was the first time that the #MeToo movement has struck at the top echelons of China's ruling Communist Party.
Here's what we know so far :
On November 2, Peng appears to have posted on China's Twitter-like Weibo damaging claims about former vice-premier Zhang Gaoli in which she alleged that he had coerced her into sex during a long-time on-off relationship.
There has been no response from Zhang, who is in his seventies.
Peng's post was soon deleted, but not before social media users took screenshots. Those were censored on China's heavily vetted Internet and still are.
But Peng's allegation was posted to Twitter -- which is banned in China -- allowing it to reach a worldwide audience.
Peng still comes up on search results online in China, but her allegations do not, and searches for her and Zhang together also show up nothing.
On Twitter, #WhereIsPengShuai began to gain traction, with tennis players past and present using the hashtag to voice concern for her.
Four-time Grand Slam champion Naomi Osaka wrote that she was "in shock". Men's world number one Novak Djokovic told reporters: "Honestly, it's shocking that she's missing."
The Women's Tennis Association (WTA) called for Peng's allegations to "be investigated fully, fairly, transparently and without censorship".
WTA chairman Steve Simon said that he had been told "from several sources" that Peng was safe.
China's tennis association did not reply to AFP requests for comment and the foreign ministry also declined to comment.
There was a new twist when China's state-run CGTN published a screenshot on Twitter of what it said was an email from Peng to the WTA in which she purportedly claims that her accusations were "not true" and she is "resting at home and everything is fine".
But doubts were quickly flagged about the awkward language and a cursor visible in the screenshot. Simon said it "only raises my concerns".
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