Scientists in the far-eastern city of Khabarovsk caught fish with bleeding ulcers in the Amur and were still trying to determine what poisoned the fish.
A concentration of heavy metals exceeding the norm for human consumption has also been found in fish.
Fishing in the Amur has been banned since November after an explosion at a factory in northeastern China poured tons of dangerous chemicals into a tributary of the Amur.
Traces of pollution were found in the Amur in December, but tests determined they presented no danger to people. Russian scientists say the danger may rise with the spring thaw as large concentrations of chemicals are believed to be frozen in the river's ice.
A slick of toxic benzene and other chemicals is moving from China's Songhua River toward the Amur River in Russia's Far East. Russian authorities fear the consequences when the 80-kilometer-long toxic slick reaches the city of Khabarovsk, which relies on the Amur for its water supply.
Officials say supplies of clean water and filtering charcoal are being stockpiled in Khabarovsk. Russian authorities have warned that more than 1 million people living along the Amur could be affected by the contaminants. The spill is the result of an explosion on November 13, 2005, at a Chinese chemical plant in the city of Jilin....(more)