Trading in the shares of Chinese conglomerate and Club Med owner Fosun International was suspended on Friday, amid reports that its billionaire chairman had become unreachable and could be under investigation.
Guo Guangchang, 48 and dubbed "China's Warren Buffett", had been out of contact since Thursday, respected business magazine Caixin reported on its website.
It cited social media postings as saying police took Guo away at an airport in Shanghai, but it was not clear whether he was put under investigation himself or assisting an inquiry.
Chinese authorities have launched wide-ranging probes into the financial sector following a market rout earlier this year when a debt-fuelled bubble -- encouraged by officials -- burst.
Guo is China's 17th richest person with a net worth of $5.6 billion, according to Bloomberg News.
The Fosun Group is one of the country's biggest private companies and its flagship subsidiary, Fosun International, has net assets of 50 billion yuan ($7.8 billion).
Trading in its shares will be halted from Friday "pending the release of an announcement containing inside information", it said in a statement to the Hong Kong stock exchange, where it is listed, as did another of the group's units, Fosun Pharmaceutical.
Several other Fosun Group subsidiaries also halted trading on the Shanghai stock exchange.
Tina Law, a spokeswoman for Fosun, declined to confirm reports that Guo could not be reached as it was "sensitive information that affects stock prices", but told AFP that the company's operations were "all normal".
Fosun has interests in property, finance, pharmaceuticals, steel and entertainment, and has been aggressively buying assets in Europe and North America.
It bought renowned French holiday company Club Med earlier this year and in April was part of a consortium that acquired Canadian entertainment juggernaut Cirque du Soleil.
It also has a stake in British-based tour operator Thomas Cook.
Rumours that Guo was being investigated have emerged several times before amid Chinese President Xi Jinping's high-profile anti-corruption campaign that has ensnared a long list of senior as well as lower level officials, including the country's former security chief Zhou Yongkang.
When Wang Zongnan, head of state-owned Shanghai retailer Bailian, was sentenced to 18 years in prison for embezzlement and bribery in August, the verdict named Guo as having a relationship with him, according to Caixin.