SHANGHAI - China's stocks fell by the most in six weeks on Thursday, as a measure of manufacturing weakened and Credit Suisse Group AG said funding might be tightened for property developers.

China's manufacturing might shrink for a third month in September, the longest contraction since 2009, after a preliminary index of purchasing managers, released by HSBC Holdings Plc and Markit Economics, showed measures of export orders and output declined.

The preliminary reading of 49.4 compares with the final reading of 49.9 for August and 49.3 for July. A reading below 50 indicates a contraction.

"Companies' earnings will slide in the third quarter as tight monetary policy curbs economic growth and increases lending costs," said Yang Delong, a fund manager at China Southern Fund Management Co, which oversees $21 billion.

The Shanghai Composite Index lost 2.8 percent to 2443.06. The measure has slumped 13 percent in 2011, extending last year's 14 percent plunge. The CSI 300 Index dropped 3.1 percent to 2686.69 on Thursday.

Stocks on the Shanghai gauge trade at 11.2 times estimated profit, matching the lowest level on record set on Monday, according to data compiled by Bloomberg.

The pace of the nation's economic growth will see a "noticeable" decline in 2011 to 2015 compared with the previous 10 years, Li Daokui, an adviser to the People's Bank of China, the central bank, said in an interview with Internet portal netease.com.

It would be unrealistic to expect growth of above 9 percent in the next three years although expansion may be above 8 percent, he said.

A gauge tracking energy producers in the CSI 300 Index slid 3.2 percent. China Shenhua Energy Co, the biggest coal producer in the country, retreated 3.4 percent to 25.68 yuan ($4).

China will levy a tax on resources based on their value and volume, according to a statement on the government's website. The country currently imposes resource taxes on producers of oil, natural gas and coal based on volume.

The tax increase will cut profits of oil explorers and coal miners.

The Shanghai Stock Exchange Property Index sank 4.2 percent, the lowest close since March 2009.

Reuters reported that the China Banking Regulatory Commission ordered trust companies to inform the regulator of business dealings with Greentown China Holdings Ltd, which may be a sign that China is trying to restrict financing sources for developers, Credit Suisse analyst Du Jinsong said on Thursday.

"If the Greentown news was true, investors are worried that the regulator will further tighten developers' financing through trust funds," said Johnson Hu, a Hong Kong-based property analyst of CIMB-GK Securities Research. "Financing through trusts accounts for quite a big piece of developers' total financing."

Greentown said in a statement it hasn't received a notice from the banking regulator and there is no investigation into the group.

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