The China Securities Regulatory Commission said it is probing “a massive sell-off” after sharp dive in the market on July 27.

The CSRC said it had received whistle-blower reports and market monitoring reports, and had organized inspection and enforcement teams.

The Shanghai Composite index lost almost 8.5 percent on July 27, the largest daily loss in eight years, followed by another 1.68 percent loss on July 28.

Regulators have previously said that “malicious short sellers” will be severely punished, and investigations against short selling and market manipulation have been conducted nationwide, according to the Ministry of Public Security.

No results of the investigations have been released.

China’s stock market has seen wild swings in the past six weeks as it plunged some 30 percent from mid-June to early July before rebounding by about 15 percent after regulators took a slew of measures to boost market confidence and avoid risks extending to more sectors.

Shares of some 2,000 companies listed in Shanghai and Shenzhen dropped on July 28, particularly those in the construction, technology and machinery sectors.

Shares of brokerages and lenders outperformed those from other sectors, posting gains of more than 2 percent on average on July 28.

Market insiders said the A-share market was adjusting on July 28 after the huge plunge, and they remained bullish for the mid-to long term, but it may take some time for investors to adjust their strategies and recover confidence.

“I have observed that investors have concerns, worrying that government supports and interventions may not last long,” said Zhang Ming, an account manager with Xiangcai Securities, a Changsha-based brokerage.

“July 27 was a result of the concerns that those who have taken profits after the three-week rally will withdraw.”

Wang Jie, an analyst with Sealand Securities, said that on the positive side, the market is becoming more rational after the wild swings.

It may take some time for the economy to adjust and find a new engine of growth, and listed companies need to boost their performance to give share price growth real support.

“Reforms across all sectors have been ongoing and may contribute more to economic growth in the second half of the year and inspire more confidence,” said Wang.