Market regulators and officials have been shouting themselves hoarse warning investors of the risks in the stock market, but it seems to have fallen on deaf ears.

And, some people have indeed made a lot of money as the benchmark Shanghai Composite Index has jumped 86 percent since October, closing at another record high of 3319.14 points yesterday.

In such heady times, it's difficult to remember that what goes up will come down. Ask those who bought shares in Hangxiao Steel Structure. They have learnt this the hard way.

Shares in the Zhejiang construction firm fell by their 10 percent daily limit yesterday after the regulators launched an investigation into the rather irregular trading pattern of the stock.

Hangxiao's shares more than tripled to 13.79 yuan by Wednesday, from 4.14 yuan on February 9, propelled at first by market talk and then by announcements from the company about a 34.4 billion yuan contract in Angola equal to about one-tenth of that country's gross domestic product.

Within a minute of starting trade, Hangxiao plunged to 12.41 yuan yesterday, its lowest daily limit, and remained there throughout the session, after the firm said in a statement that the stock market watchdog wanted it to cooperate with investigations.

As evidenced by the thin trading volume, the stock found few buyers, with the market fearing more losses for those who bought the shares this week.

Even though the securities watchdog did not give a verdict on whether the company was involved in any irregular trading and the company claimed that the investigation was propelled by the volatility of its shares, most seem to think otherwise.

An online survey conducted by leading Chinese portal Sina.com yesterday showed 94.2 percent of the 43,837 respondents saying Hangxiao's trading pattern looked suspicious and 58.3 percent casting doubt on the 34.4 billion yuan contract.

The Hangxiao case just goes to prove, once again, that there is still a long way to go as far as transparency of the stock market is concerned.

Despite the recent regulatory efforts to strengthen corporate governance and disclosure of detailed information, there are plenty more loopholes to be plugged in the market.