One of China's richest men, Guo Guangchang, is reported to be missing.

Financial magazine Caixin said that staff at Mr Guo's company, Fosun International, had been unable to contact their boss since Thursday afternoon. 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).