Emergency measures are in force in the north-eastern Chinese city of Harbin, after water supplies were turned off.
Thousands of tons of water are being shipped in by road
The move came amid fears the city's drinking water could be contaminated after an explosion at a chemical factory upstream of the Songhua river.
Authorities in Harbin, home to 3.8m people, said the shut-off would last four days - though there are fears it could go on longer.
Schools and many businesses have shut, while flights from Harbin are sold out.
"Everyone wants to leave Harbin and it is very difficult to buy tickets," a factory manager told Reuters.
The chemical factory processed benzene, a highly poisonous toxin that is also carcinogenic.
Fifteen hospitals have been placed on stand-by to cope with possible poisoning victims.
More than 16,000 tons of drinking water is being brought in by road, the Chinese state news agency Xinhua said - though this is less than Harbin's residents habitually use in a day.
The government initially said the stoppage would last four days, but a water company official has told the BBC there is no set timetable for the resumption of supplies.
BBC Beijing correspondent Louisa Lim says residents of Harbin are mistrustful of government statements, having originally been told the stoppage was for routine maintenance.
The initial announcement of water stoppages led to panic buying of water and food, sending prices soaring.
Bottled water sold out at supermarkets and other shops in the city, but the China Daily reported that other beverages, including milk, were still available.
"All containers are being used to store water, including the bathtub. It will be OK for four days, but not longer than that," a factory manager said.
Local media showed pictures of dead fish in the Songhua River
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.
Five people were reported to have been killed in the blast, and more than 60 injured.
The explosion forced the temporary evacuation of some 10,000 residents, but people have since been allowed to return home.
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.
The authorities said there was no sign that the city's water supply had been contaminated, but the Beijing News showed pictures of dead fish washed up on the banks of the Songhua river near Jilin city.
Harbin is in China's north-east Heilongjiang province, and is one of the country's coldest cities, with overnight temperatures this week falling to -12C. It hosts an ice and snow festival each January.
Are you in the area? Have you or anyone you know been affected by the decision to cut off the water supplies? Send us your comments using the form below:
My son is an exchange student in Harbin. They have been told not to use the water for 10 days including showers, etc. Water from local wells are OK. All water is sold out, but fortunately, the locals haven't discovered Gatorade. Any confirmed details would be appreciated.
Charlie Goodrich, Lexington, MA, USA
At first glance, the Harbin city authorities look not candid enough towards the residents. However, compared with all the other cities along the Songhua river between Jilin and Harbin, all of which should have already been affected by the polluted river water and yet have been quiet on this, the Harbin city authorities are still doing a better job.
theo (Chinese national currently living in Singapore),
I am just waiting for any news on this. My sister is in Harbin teaching and sent me a flurry of disturbing emails- the most perturbing is that there is brown oily water that smells of urine coming out of her pipes. Also some officials have left the city where she is. She has yet to respond to my seven emails and I am eagerly awaiting any news. She also said that she believes that they have known about this water situation days before announcing it.
Kem Kramer , Toronto
I have my oldest brother who is currently working in Harbin, China. We contact him every couple of days and he has let us know of the devastation that is occuring due to there been no water. He has been told the shower he had the day before yesterday is the last one until the end of the week at the earliest. He lives with four other English boys, as they are all teachers working to teach Chinese children English. They had been told that there was no water but not given enough time to save clean water for them to live from. There seems to be a lot of anguish across the country but at least we know he is well so far. we just hope that the showers they all had when the chemicals went into the system will not harm them in any way.
Victoria Hutchinson, Redcar, England
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