China brokerage shares fall on probe Shares of China's largest brokerage, state-owned Citic Securities, fell as much as 4% after it said three executives, including its president, were under police investigation.The executives are being investigated for suspected insider trading and "leaking inside" information.The probe comes as Beijing intensifies the scrutiny on irregular stock trading that has rocked Chinese shares.Mainland Chinese shares have lost about 40% of their value since mid-June.