An investigation into irregular trading of shares of Zhejiang Hangxiao Steel Structure may underline the risks inherent in China's stock market boom. The China Securities Regulatory Commission is investigating irregular trading of the company's shares after prices jumped the maximum daily limit in 12 of the last 13 trading sessions, the South China Morning Post reported. The stock price has tripled in three months. Two weeks ago, the company announced it had won a US$4.4 billion (RMB34.4 billion) contract to build a housing project in Angola. The announcement sparked a virtually unprecedented climb until the CSRC announced its investigation. The share price fell the maximum 10% Thursday. Industry insiders were sceptical of the company's ability to handle the contract and cast doubts on the unusual movement of the stock, prompting speculation that it has been manipulated by investors.