China Star Entertainment (HKG:0326) flagged a high concentration of shareholding in the firm's shares following a request from the Hong Kong Stock Exchange, according to a bourse filing Monday.

Shares of the film production company fell over 19% in recent late-morning trade.

According to the notice, 19 shareholders plus China Star's chairman and vice chairman controlled 91.37% of the company's issued share capital, leaving only 8.63% of the issued shares in the hands of other shareholders.

This meant that the shares may not have a genuine market and prices could fluctuate "substantially" even with a small number of shares traded, China Star said.