CHANGSHA, April 2 (Xinhua) -- More than a hundred paper mills that discharge chemical-laden waste into Dongting Lake, China's second largest fresh-water lake, were ordered closed on weekend after they failed to live up to promises to reduce pollution.

    "We tried to allow production while making efforts to control pollution, but the practice hasn't been effective." said Jiang Yimin, director of Hunan Provincial Bureau of Environmental Protection.

    "Production won't be allowed to resume until a paper mill operator can control pollution and meet pre-set requirements for waste water discharge," said Jiang.

    The 2,800 sq km Dongting Lake, which flows into the Yangtze River, the country's longest river, has been plagued by pollution which has caused a decline in marine life and the spread of schistosomiasis among people.

    Of the more than 100 paper mills whose waste water ends up in the lake only two have met pollution discharge requirements. The mills, which are mainly in the cities of Yueyang, Yiyang and Changde, discharged 100 million tons of waste water into Dongting Lake last year, threatening marine life and the source of the region's drinking water.

    Paper mills that fail to meet pollution discharge standards by the end of the year will be permanently shut down, Jiang said.