Bao Fan, the CEO of China Renaissance Holdings has not been able to be contacted in recent days, the firm said during a market update.
Bao is a leading stockbroker in China, whose clients include major technology companies Didi and Meituan.
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The announcement has renewed concerns about a possible repression by the Chinese government against personalities from the financial and technological world.
Shares of the investment firm plunged on Friday after shareholders learned that "Bao Fan could not be contacted."
The board added that it was not aware of "any information indicating that Bao's unavailability is or could be related to the business and/or operations of the group."
When the BBC asked company representatives for more details, China Renaissance forwarded the announcement it had already published on the Hong Kong Stock Exchange.
The company did not specify how long he has been missing.. However, the Chinese business news service Caixin he cited sources who said staff had not been able to contact him for two days.
The statement also reported that the company's chairman, Cong Lin, was detained by authorities last September for his previous work at the state-owned ICBC bank.
China Renaissance appears to have had no comment on Cong's situation. He is no longer listed as an executive on the company's site or in its most recent interim report.
The disappearance of Bao, one of China's top technology investors, adds to the list of Chinese executives who have suddenly disappeared for periods without explanation.
According to the magazine Forbes, at least half a dozen billionaires have gone missing for periods in recent yearsafter reporting clashes with the Communist Party of China.
In several cases, it was suspected that they had been involved in investigations of corruption, tax or other misconduct.
The absences include Fosun Group founder Guo Guangchang, known as China's Warren Buffet, who disappeared for several days in 2015.
Chinese-Canadian businessman Xiao Jianhua was also kidnapped in 2017. He had been one of the richest people in China and was jailed last year for corruption.
At the end of 2020, Alibaba founder Jack Ma also disappeared for three months, after making critical comments with market regulators. He had planned to go public with his digital payments firm Ant Financial, which would likely have made him the richest man in China.
Bao is seen as a titan in China's tech industry, by running many of the businesses that have shaped the country's online consumer economy. He founded China Renaissance in 2005 after a banking career at Morgan Stanley and Credit Suisse.
His company was behind historic dealsincluding Tencent's strategic investment in JD.com, and mergers of ride-sharing powerhouses Didi and Kuaidi, advertising sites 58.com and Ganji, and food delivery giants Meituan and Dianping.
China Renaissance has also advised the initial public offerings of e-commerce sites JD.com and Kuashou, as well as Didi's listing on the New York Stock Exchange in 2021.
In a 2018 article, Bao wrote that his company was somehow connected to 70% of internet companies known to the Chinese public.