Fosun, one of China`s biggest private conglomerates, halted trading of its Hong Kong shares following the reports.
There is speculation that Mr Guo, described as China`s Warren Buffett, has been detained by the police.
Caixin quoted social media messages saying he had last been seen with police in Shanghai.
A source close to the Fosun Group told the BBC that Mr Guo had not been contactable via an internal company-wide mobile app.
"It`s very likely he`s been asked by the Chinese authorities to co-operate in an investigation. He is not being investigated himself," the source said.
He declined to speculate about the details of the investigation.
Fosun said it would release further details later. Mr Guo was linked to a corruption court case in August.
BBC Asia-Pacific analyst Michael Bristow says Mr Guo`s empire extends across the world, while the publisher Forbes estimates his fortune at $7bn (£4.6bn).
Fosun Group has interests spanning media, insurance, real estate and retail. Recently, it took control of French holiday group Club Med.
Fosun International, the parent company of Shanghai-based Fosun Group, was listed in Hong Kong in 2007.
In a statement to the Hong Kong stock exchange on Friday, the firm said its shares would be halted from trade "with effect from 9:00 on Friday, 11 December 2015 pending the release of an announcement containing inside information".
As part of the statement, Mr Guo`s name was included in the list of Fosun`s executive directors.
If Mr Guo has indeed disappeared, he wouldn`t be the first high-profile executive in China`s financial sector to have gone missing in recent weeks.
There is speculation that this is part of the wider anti-corruption campaign that Beijing launched to clean up various pillars of China`s economy - which now includes the financial sector.
If Mr Guo is proved to be part of that, then he would be among the most high-profile Chinese businessmen caught up in it.
He called himself a student of the US investment legend Warren Buffett and wanted to transform his conglomerate, Fosun, into a top asset management firm.
Fosun has made a number of international acquisitions recently and is a shareholder in global media companies such as Forbes. It is seen as one of China`s most successful firms internationally.
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