In November, the China Central Disciplinary Inspection Committee (CCDI), the Communist Party's top graft-busting body, announced it was investigating Yao Gang, a deputy head of the China Securities Regulatory Commission (CSRC) for suspected "serious breaches of discipline", the usual euphemism for corruption.

Investigators are probing whether Yao leaked classified information about the government’s market rescue to executives at brokerages including Citic Securities  (>> CITIC Securities Company Limited)<6030.HK> and Guotai Junan Securities Co (>> Guotai Junan Securities Co Ltd) so they could buy stocks before they were purchased by state funds, the Wall Street Journal said, citing officials with knowledge of the matter.

Representatives from Citic Securities and Guotai Junan weren't available for comment. The CCDI also wasn't available for comment. The CSRC didn't immediately respond for comment.

Zhang Yujun, the assistant chairman of the securities regulator, also was put under investigation for "serious violation of discipline", the graft watchdog said in September.

Chinese brokerages, including Citic Securities, late last month said they were being investigated by the CSRC for suspected rule breaches related to the signing of margin trading contracts.

Guotai Junan Securities, along with Haitong Securities (>> HAITONG Securities Company Limited)<6387.HK>, also are being probed by anti-corruption investigators, the official Xinhua news agency reported in November.

In September, the CSRC also said it would punish Founder Securities (>> Founder Securities Co Ltd), GF Securities (>> GF Securities Co Ltd), Haitong Securities, and Huatai Securities (>> Huatai Securities Co., Ltd.) following an investigation of the brokers.

(Reporting By Matthew Miller; Editing by Sam Holmes)