An investor is seen at a trading hall of a securities firm in Shanghai, June 24, 2013. Chinese shares plunged on Monday and closed below a key psychological mark over worries about the liquidity crunch in the financial system and subdued strength in the world's second largest economy. The benchmark Shanghai Composite Index tumbled 5.3 percent to end at 1,963.24, the lowest point in nearly seven months, while the Shenzhen Component Index pummeled 6.73 percent to 7,588.52.