The major Chinese city of Harbin is facing four days without water because of an unexpected mains stoppage.
A chemical blast has been blamed for the problem
The announcement that water supplies would be cut off from Tuesday has sparked panic-buying of bottled water and other drinks at local supermarkets.
There is confusion over why the authorities are cutting off the water.
Xinhua agency cited fears it had been contaminated by a chemical blast, but the China Daily quoted the government as saying it was for mains maintenance.
Water, various other drinks and even milk were all reported to have sold out at large supermarkets in the city.
There are also reports that some people have been sleeping outside in sub-zero temperatures after rumours of an imminent earthquake.
The order to cut off the water comes after a 13 November explosion at a petrochemical plant in Jilin city, about 380km (230 miles) up the Songhua river from Harbin.
More than 60 people were injured in the blast, with 23 still in hospital, according to the French news agency AFP.
The explosion reportedly forced the temporary evacuation of some 10,000 residents, but the authorities gave no indication in the state media at the time that there were pollution fears.
However, the China Daily reported on Tuesday that the government had issued two statements. One simply spoke of water main maintenance and repair, but the other mentioned the Jilin blasts.
Harbin Water Supply Company refused to comment, the paper said.
But sources at the environment bureaux in Harbin said the water quality there was normal, and Jilin's local environment bureau also found the water barely affected after the blast.
Harbin, in China's north-east Heilongjiang province, is home to at least three million people. It hosts an ice and snow festival each January.