Fast-spreading, foul-smelling blue-green algae on Taihu Lake last week turned tap water yellow and smelly in the riverside city.

"Those enterprises exceeding emission standards for phosphate and nitrate have to stop their production immediately," said Zhang Lijun, deputy director of the State Environmental Protection Administration.

Zhang told a press conference in Beijing that his agency has also asked the Jiangsu provincial government to stop approving new factories that discharge phosphate and nitrate.

He said the lake's nitrogen content tripled between 1996 and last year, while the content of phosphate pollutants increased 150 percent.

SEPA will investigate all enterprises releasing nitrogen and phosphate pollutants in the area, authorities said. Those exceeding emission standards will be shut down, and production restrictions will be imposed on the rest according to the lake's water quality.

The algae in Taihu Lake resulted in the suspension of tap water supplies to the residents of Wuxi.

Workers have collected 6,000 tons of algae from the lake, according to a Wuxi official.

"The city is facing more risks of algae bloom in the future. Local governments should make an emergency response plan to deal with the outbreak," Zhang said.

The Taihu, Dianchi and Chaohu lakes and the Liaohe and Haihe rivers suffered from serious pollution in 2006. The Songhuajiang, Yellow and Huaihe rivers had medium contamination.

Zhang blamed industrial and household sewage and the excessive use of fertilizers as the major sources of water pollution. He said the government will launch stricter discharge standards for industries, upgrade sewage treatment facilities and control the use of chemical fertilizers.

"The safety of drinking water is our priority in environmental protection," Zhang said. He said China should see a "turning point" this year in its anti-pollution efforts and will likely meet its clean air and water goals in coming years, adding that the emission of major pollutants in China will decrease in 2007.

"We will achieve the goal of reducing the emission of major pollutants by 10 percent during the 11th Five-Year Plan period (2006-2010)," Zhang said.

China failed to reach its goal of cutting the emission of sulfur dioxide and chemical oxygen demand, a measure of water pollution, by two percent in 2006.

Zhang said that while the amount of ammonia and nitrates in waterways increased in 2006 and overall air quality declined, protection measures will soon make an impact.