Police have confirmed that one of China's richest men, Huang Guangyu, is being held in custody while he is investigated for "economic crimes".
Mr Huang, 39, went missing last week and shares in his company, Gome Electrical Appliances Holdings, have been suspended from trading.
Officials gave no further details, but Chinese media report there have been irregularities in the share price of a company controlled by his brother.
The billionaire electrical appliance tycoon is worth $US6 billion.
The BBC reports that the announcement of the arrest was the first official confirmation of widespread reports that Mr Huang was being questioned for share trading violations or other crimes.
Gome says its operations are not affected by Mr Huang's situation, but has refused to make further comment.