A second wave of pollution from last year's toxic chemical spill in China is affecting rivers in Russia's Far East, according to environmental experts.
Water supplies were cut off after the spill in November
They say chemicals trapped in a frozen river during the winter are now being released by the spring thaw.
People in the city of Khabarovsk and other settlements along the River Amur have noticed strong chemical smells.
Russian officials said higher than permissible levels of chemicals have been detected in the river.
People have been advised to stop using tap water for drinking or cooking.
The original spill occurred in November, when large amounts of benzene, phenol and other toxic substances were found in China's Songhua river.
The spillage followed an explosion at a chemical factory.
The incident strained relations with Russia and focused attention on pollution problems in China's rivers.
The Songhua feeds into the Amur on the Russian border, affecting water supplies for more than 500,000 people in Khabarovsk.
In March China said it would spend more than $1.2bn cleaning up the Songhua.