China's securities watchdog announced Thursday it will investigate suspected manipulation of the stock market following weeks of plummeting stocks and future markets.

Zhang Xiaojun, spokesman of the China Securities Regulatory Commission (CSRC), said they will investigate possible illegal activities occurring in multiple markets. He said they have tracked irregularities between securities and futures trading.

The CSRC will transfer any criminal cases to the police, Zhang said.

The announcement came after the losing streak in China's A-share market continued, making people point to conspiracy.

Shares continue their descent on Thursday. The benchmark Shanghai Composite Index fell 3.48 percent to finish at 3912.77 points.