The Russian city of Khabarovsk is bracing for the arrival of a chemical river spill, after a massive leak of toxic benzene upstream in China.
Khabarovsk residents have been preparing for weeks
Chinese and Russian workers are racing to complete a dam, but an official says sandbags are being washed away as quickly as they are laid.
The spill was caused by an explosion at a Chinese chemical factory last month.
Khabarovsk residents have been stocking up with drinking water for weeks, and the city is reported to be calm.
The first traces of benzene are expected to reach Khabarovsk, on the Amur river, within hours.
The contamination is estimated to cover 190km (119 miles) of river, and will take several days to pass through the city.
Samples from the river are being assessed constantly, the authorities said, promising to keep the public informed on the danger to health.
Water supplies to 3.8 million people in China's Harbin city were cut off for five days after the leak.
The explosion occurred higher up the Songhua river, in Jilin. The Songhua flows into the Amur river on the Russian border.
Viktor Ishayev, governor of the Khabarovsk region, said he would be seeking compensation from China to pay for emergency measures, like treating the benzene with activated charcoal.
"We are spending money constantly," he said.
"People are working on this every day. So of course all of this money will be added up in order to demand compensation."