Tap water for the 3 million residents of the Chinese city of Harbin were turned off Wednesday as a chemical spill from upriver approached in the Songhua river.
A spokesman for the Heilongjiang provincial government said the toxins approaching were high-density benzene and nitrobenzene, expected to arrive early Thursday.
"Benzene levels were 108 times above national safety levels," China's Environment Protection Administration said.
The city ordered schools and businesses closed, and all available tickets for bus, train and air travel out of the city were snapped up.
Fifteen hospitals were placed on stand-by to cope with possible poisoning victims.
More than 16,000 tons of drinking water was being brought into Harbin by road, according to the Chinese state news agency Xinhua, although that is less than Harbin's residents use in one day.
Downriver, Russian officials are also on alert in towns further down the Songhua, which is called the Sungari river in Russian, UPI reports.