An investigation team led by China's Vice Minister of Public Security Meng Qingfeng has found clues that certain trading firms have suspectedly manipulated futures trading in the stock market.

The team is currently carrying out further probes. It did not give other details.

The investigation team visited the head office of the China Securities Regulatory Commission on Thursday morning to investigate what it called "malicious short-selling of stocks and stock indices", an example of the dodgy practices many believe were part of the recent stock over the past few weeks.

The team arrived in Shanghai on Friday to search for further clues on such illegal practices.

After China's key stock index plunged by over 30 percent from its June 12 peak, the government has stepped in with various measures to save the market, including pouring in funds and restricting futures trading on a major small-cap index.

On the back of the supportive measures, the stock market staged a strong rebound for a second consecutive day on Friday, with the benchmark Shanghai Composite Index surging 4.54 percent to end at 3,877.8 points.