Researchers extracted samples at nine sites along the Ergun, Heilongjiang, Wusuli and Suifen rivers and the Xingkai Lake, and have finished lab analysis based on each country's standards, sources with the State Environment Protection Administration (SEPA) said.

    Data were gathered on chemical oxygen demand (COD), contents of heavy metals, pesticides, riverbed mud to determine water quality in the cross-border water bodies.

    The two sides have also exchanged statistics and will meet again in the near future to discuss specifics on what work needs to be done on which sections of the rivers.

    It is second joint operation this year since China and Russia signed the Joint Monitoring Plan on Border Rivers in 2006, after an explosion at a Chinese chemicals plant sent nitrobenzene and other chemicals into the Songhua River that flows into the Heilongjiang in 2005.

    The contamination forced Harbin, capital of Heilongjiang in China's northeast, to temporarily stop water supply to 3.8 million residents.

    The plan requires both sides to operate the testing program for five years from 2007. The first such test was carried out in June this year.

    Before the plan, joint river monitoring work had been carried out at lower levels between the Heilongjiang province and Russia's Khabarovsk since 2002.