Rescue teams in north-east China are working to retrieve 3,000 barrels of chemicals washed into a major river, state media say.
Severe floods washed the barrels, from two chemical storage facilities, into the Songhua river in Jilin city.
Around 400 barrels have been recovered so far by workers at eight stations on the river.
Water quality was being checked and no chemicals had yet been found in the water, state media said.
Several parts of China have been hit by flooding in recent weeks, amid the worst seasonal rains in a decade.
Elsewhere in Jilin, 30,000 people in the town of Kouqian were said to be trapped by floodwaters after a reservoir and two rivers burst its banks.
The Songhua River is the largest tributary of the Heilongjiang river, also known as the Amur river in Russia, on the China-Russia border.
Xinhua news agency said that a total of 7,000 barrels from the storage facilities of two chemical plants had been washed into the river.
Four thousands of the barrels were empty, the agency said. The remaining 3,000 contained flammable chemicals, it said.
Water supplies in the city of 4.5 million people were briefly suspended and panic-buying reported as residents stocked up on bottled water.
But by Thursday morning water supplies had been mostly restored, reports said.
Water quality in the river was being monitored at seven stations, Xinhua news agency said.
"Some residents are worried, but we have yet to find any leaks in the barrels of chemicals, so they should not be worried about their water quality," an official with the Jilin Water Bureau, who did not want to be identified, told AP news agency.
Russian authorities were also checking the water in the Heilongjiang river (the Amur river), a report on Russian television said.
Five years ago a chemical spill in the Songhua river left the city of Harbin and its 3.8 million residents without water for five days.