China's stocks tumbled heavily in the afternoon session on Friday, with the benchmark Shanghai Composite Index nose-diving more than four percent.
Brokerages led the diving. CITIC Securities once hit the daily drop limit of 10 percent, while 19 companies tumbled over six percent, Xinhua reported.
On Thursday night, CITIC Securities and Guosen Securities released statements that they are under investigations by the Securities Regulatory Commission.
Media reported that another brokerage giant Haitong Securities is also being investigated by the national regulator.
The company's share trading was suspended this morning.