Tennis great Roger Federer voiced concern Saturday for missing Chinese player Peng Shuai.

Peng, a two-time Grand Slam champion and former No. 1 in doubles, disappeared after making allegations of sexual assault more than two weeks ago against former vice premier Zhang Gaoli.

“She’s one of our tennis champions, a former world No. 1, and clearly it’s concerning,” Federer told Sky Italia . “I hope she’s safe. The tennis family sticks together and I’ve always told my children as well that the tennis family is my second family. I’ve been on tour for 20-25 years and I love the tour, I love the people that are there, (they) are special, the players as well, and she’s one of them."

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China’s Foreign Ministry has repeatedly disavowed any knowledge of Peng’s case. Ministry spokesperson Zhao Lijian told media on Friday the issue is “not a diplomatic question and I’m not aware of the situation.”

Peng wrote a lengthy social media post on November 2 in which she said she was forced to have sex three years ago with Zhang. The post was quickly deleted from Peng’s verified account on Weibo, a leading Chinese social media platform. But screenshots of the explosive accusations were shared on the internet.

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“I’ve been in touch with (ATP Tour) president Andrea Gaudenzi as well the last days, just to get any news, any feedback of the developing story,” added Federer, who is working his way back from his latest knee surgery. “I just want her to be OK and that she’s safe and that we hear something hopefully soon.”