Serena Williams on Thursday joined the chorus of concern for Chinese tennis star Peng Shuai, whose whereabouts have been shrouded in mystery since she alleged a powerful Chinese politician sexually assaulted her. "I am devastated and shocked to hear about the news of my peer, Peng Shuai," former world number one Williams wrote on Twitter. "I hope she is safe and found as soon as possible. This must be investigated and we must not stay silent." Serena Williams' tweet was accompanied by a photo of a smiling Peng captioned with #WhereIsPengShuai. "Sending love to her and her family during this incredibly difficult time," Williams added.