Zhang Yun had stepped down from Agricultural Bank of China, the bank said in a statement to the Hong Kong stock exchange, where it is listed.
The announcement came a month after China's news portal Sina reported that Zhang, 56, had been taken away for questioning.
Yesterday, meanwhile, China's biggest brokerage Citic Securities told the Hong Kong exchange it had lost contact with two members of its executive committee - Chen Jun and Yan Jianlin - and they might be assisting an investigation.
Chinese authorities have launched a series of investigations into the financial sector after a debt-fuelled stock market bubble - encouraged by authorities - burst in the summer in a rout that wiped out trillions of dollars of market capitalisations.
Citic Securities said two weeks ago that the company itself was being probed by the market regulator, the China Securities Regulatory Commission, following police investigations into several company executives for insider trading and leaking inside information.
Agricultural Bank closed down 0.91 per cent in Shanghai on today but added 0.34 per cent in Hong Kong, while Citic Securities dropped 1.86 per cent in Shanghai and 0.33 per cent in Hong Kong.
