Women's Tennis Association Chief Executive Steve Simon has called for verifiable proof that missing Chinese player Peng Shuai is safe.
The former Wimbledon doubles champion hasn't been heard from since she made sexual assault allegations against a top government official.
"The WTA and the rest of the world need independent and verifiable proof that she is safe," Mr Simon said.
"Peng Shuai must be allowed to speak freely, without coercion or intimidation from any source.
"Her allegation of sexual assault must be respected, investigated with full transparency and without censorship."
Campaigners have cast doubt over an email that's been released by Chinese state media claiming to be from the 35-year-old.
"I'm not missing, nor am I unsafe," the email says.
"I've just been resting at home and everything is fine.
"Thank you for caring about me."
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