HONG KONG (Dow Jones)--Profit-taking after the Hang Seng Index's recent strong gains, and sharp falls on mainland China's bourses led Hong Kong shares lower Wednesday, though ample liquidity kept the benchmark index above the key 20,000 level. The blue-chip Hang Seng Index fell 489.04 points, or 2.4%, to 20,135.50 after trading between 19,787.48 and 20.542.61 during the session. Turnover jumped to HK$101.78 billion from HK$84.85 billion Tuesday, boosted by active trading in market debutant BBMG. The Chinese building materials producer rose 56% to HK$9.97 from its initial public offering price of HK$6.38, having hit an intraday high of HK$10.50. Mark To, an associate director at Prudential Brokerage, said he expects the index to stay above the psychologically important level of 20,000 in the near term on ample liquidity. 'The selling pressure was modest compared with the market's recent gains, given the strong liquidity in the market,' To said. Wednesday's declines came after the benchmark index rose 7.1% and hit consecutive 10-month highs in the previous four sessions. The falls also came amid sharp declines in China shares. China's benchmark Shanghai Composite Index plunged 5% Wednesday because of concerns about slowing credit growth and profit warnings from domestic companies. In Hong Kong, index heavyweight HSBC fell 1.2% to HK$72.80, and China Mobile ended 1.6% lower at HK$82.25. Hong Kong-listed Chinese property firms fell on concerns over Beijing's strict enforcement requirements for second-home mortgages, after mainland real-estate sales and prices had risen sharply. Guangzhou R&F fell 5.5% to HK$17 and China Resources Land dropped 3.7% to HK$18.80. 'The Chinese government may try to further tighten monetary policy, after seeing sharp rises in the sales of mainland property companies during the first half,' said Louis Tse, an investment strategist at Value Convergence. Chinese oil companies fell after Beijing cut gasoline and diesel prices by 3%. China Petroleum & Chemical Corp. fell 5% to HK$6.78, PetroChina slid 3.9% to HK$9.12 and Cnooc lost 4.1% to HK$10.42. Commodities companies fell alongside the broader market. Alumina and aluminum producer Chalco fell 6% to HK$8.59 and coal producer Shenhua fell 5.3% to HK$31.45. C C Land plunged 12% to HK$5.80 after the firm said it plans to raise HK$2.53 billion in a placement. i-Cable soared 61% to HK$1.24 after it urged the Hong Kong government to issue it with a license to provide free-to-air broadcasting services. -By Joyce Li, Dow Jones Newswires; 852-2802-7002; joyce.li@dowjones.com