Residents along the Songhua River in Northeast China received a reassuring Spring Festival gift yesterday from the country's environmental chief, who said they can safely consume its fish and drink from groundwater wells.

"The water quality of the Songhua River will not exceed national standards on a large scale during the spring thaw, and fish in the river and from pounds along the banks are safe to eat," State Environmental Protection Administration Minister Zhou Shengxian told a press conference in Beijing.

Except for trace amounts of nitrobenzene well below the national permissible standard for drinking water that were detected in individual wells, the area's groundwater is safe for drinking, Zhou said.

There had been mounting concern among some people that the spring thaw will release nitrobenzene trapped in the ice and in the sediment of the river following the November blast at an upstream chemical plant of the Jilin Petrochemical Corp, which spewed 100 tons of pollutants into the water.

But Zhou said research had indicated only a small amount of the toxic chemical had been frozen in the ice. Equally limited is the amount of the compound entrapped in the sediment because the riverbed consists largely of sand.

These factors, along with the fact that the river will become a torrent when ice melts in the spring, convinced experts of the safe water quality, Zhou said, citing an interim assessment of the river spill done by a host of Chinese institutions and agencies, which started on December 13.

Chen Jining of Tsinghua University's Institute of Environmental Science and Engineering, said: "Even in the rare cases when levels are beyond standards in some places, we also have the technology in place for example, activated carbon to ensure safe drinking water supplies."

The Jilin company is a firm under the China National Petroleum Corp (CNPC). A special team has been set up to investigate any connection between the blast and the CNPC, Zhou revealed.

Xie Zhenhua, Zhou's predecessor, resigned after the accident.

"The team is working hard, and as soon as results are available, they will be released to the public through the media," Zhou said.

Besides water quality, Zhou also guaranteed that livestock along the river banks and their products are safe to eat, and using the water of the Songhua River for irrigation will not inhibit the growth of crops.

Zhou said China will further implement the joint monitoring programme with Russia on boundary rivers. Experts predicted the front of the pollution plume would reach the estuary of the Armur River in Russia by the end of this month.

Fan Yuansheng, a division director of the environmental agency, said yesterday that China has upgraded its pollution control programme for the Songhua River, focusing on water sources of large and medium-sized cities along the river.

Through building waste water and sewage treatment facilities, promotion of clean production methods and other pollution control efforts, the country will strive to make 90 per cent of the water in the Songhua River drinkable within five years, Fan said.

Drawing lessons from the Songhua incident, Zhou's agency has begun surveying China's 21,000 chemical enterprises, more than half of which are located along the country's two major river basins, the Yellow and Yangtze. Many of the plants had not undergone environmental impact assessment and were built in residential areas or upstream from rivers, according to the survey.