shanghai former vice-chairman china securities regulator yao gang investigate take bribe official china daily say cite prosecutors office yao one senior figure arrest crackdown suspect stock manipulation late 2015 mid-year collapse chinese stock market follow long bull run yao subject coercive measure range summon surveillance detention arrest among action supreme people procuratorate say without specify face newspaper say thursday july china graft watchdog say yao would prosecute offences include take bribe destroy order capital market yao 55 general manager guotai junan securities 1999 take position china securities regulatory commission 2002 paper say csrc know king ipos oversee initial public offer chinese mainland 13 years add china probe former vice-chief securities regulator graft