Chinese shares plunged more than six percent Friday, after inquiries were announced into several major brokerage firms.

The benchmark Shanghai Composite Index slumped 6.11 percent, or 222.18 points, to 3,413.37. The Shenzhen Composite Index, which tracks stocks on China's second exchange, tumbled 6.66 percent, or 154.96 points, to 2,170.73.