Guo Guangchang, dubbed "China's Warren Buffett", attended Fosun Group's annual meeting today morning, pictures posted by business magazine Caijing showed.
The publication quoted Guo as saying "there will be a better Fosun next year" during a speech at the event, without mentioning anything about the investigation.
Guo had been out of contact since Thursday and two of the group's listed arms in Shanghai said in statements last week the 48-year-old was "assisting in certain investigations" conducted by mainland authorities.
Caijing said today that Guo has "finalised" assisting in the inquiries and "returned home safely".
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It was not immediately clear what the investigation was in relation to, but it comes as China targets the financial sector as part of a sweeping anti-graft campaign following a stock market rout that rocked global markets over the summer.
Fosun spokeswoman Valentina Wu declined to comment when contacted by AFP today.
Fosun Group is one of China's biggest private companies, and has interests in property, finance, pharmaceuticals, steel and entertainment, and has been aggressively buying assets in Europe and North America, including Club Med.
Other reports said he was being questioned in connection with a probe into former Shanghai vice mayor and director of the Shanghai Free Trade Zone Ai Baojun, who was placed under investigation last month by the Communist Party's internal anti-graft body for "severe disciplinary violations", a euphemism for corruption.
Ai's wife was allegedly investigated on suspicion of manipulating the stock market. She died of kidney failure a week before Ai fell.
Since coming to power Chinese President Xi Jinping has waged a much-publicised anti-corruption campaign that has ensnared a long list of officials, including the country's former security chief Zhou Yongkang.