CHUNKS of greyish-white ice float along the pockmarked skin that forms the surface of the Songhua river. Underneath is a 50-mile tongue of toxic chemicals oozing through the freezing water.

The slow-flowing river gave off no scent of its contamination yesterday. But the arrival of the poison has spread fear among millions of residents of Harbin, China’s northernmost city, and forced officials to turn off water supplies for the first time in half a century.

In Li Xiaohe’s home in a rundown corner of the industrial city, basins and buckets filled with water cover the floor. The bath tub is also full. The three-year-old girl bounds through the small flat, excited to be home after the Government closed all schools until Monday. “We’ve filled up everything we have,” said her grandmother, Xiu Songyuan, a retired teacher.

Mrs Xiu is taking no chances with her granddaughter’s life. Like many of the city’s nine million residents faced with benzene, a carcinogenic solvent, flowing through the centre of the city for up to three days, she is leaving. The family owns a primitive home in the countryside, and Mrs Xiu packs quilts, powdered milk, bananas and long underwear into plastic bags and crams the children into a neighbour’s car. “We have our own well at our house in the country and it’s better to take the children there for a few days,” she says. “It’s almost like a holiday.”

Other families were also trickling back to long-abandoned homes in the village until the Government turns the taps on again. Each home gets water from the village well. “This water is really pure and safe,” Mrs Xiu said.

The Environmental Protection Administration said that it would take about 40 hours for the slick to flow through Harbin. City officials promised that the water would be safe to use after four days, and that it should be flowing through Harbin’s pipes again at the weekend. “I will drink the first sip of water when it is turned on,” said Zhang Zuoyi, the Heilongjiang provincial governor, in an effort to calm fears. Officials also announced the drilling of 100 new wells and the reopening of 400 old ones.

About 3.8 million of Harbin’s citizens have no water, and those unable to escape worry that the Government may not keep its word. Jiang Duyi, a restaurant owner, said that he would have to close because his water tank would run out in three days. “I don’t have family in the country so I can’t run away.”

Thousands of others have fled by train or aircraft. Most trains leaving the city are full, and no air tickets are available until the weekend, despite additional flights. The city is bringing in millions of bottles of water. Mountains of them fill supermarkets, hawkers pile supplies on pavements and military tankers supply blocks of flats.

Having initially given no reason for the decision early this week to cut off the water, thus sparking panic buying and rumours of an earthquake, officials have since issued constant updates on the crisis and assurances that residents’ safety is paramount. They warn residents to be alert for symptoms of benzene poisoning, which can cause anaemia and kidney and liver damage. Hospitals are on standby.

An estimated 100 tonnes of benzene and other chemicals spewed into the river after an explosion at a petrochemical plant in neighbouring Jilin province two weeks ago. The environmental administration said that the river contained 100 times more than the normal levels of chemicals.

The benzene spillage is the latest in a series of accidents that highlight the dangers posed by factories in China more concerned with profit and economic growth than with safety.

And the Songhua river flows for thousands of miles beyond Harbin. In Russia, the far eastern region of Khabarovsk is expected to declare a state of emergency today amid fears that water supplies for 1.5 million residents will be contaminated. The slick is expected to flow along the Songhua into Russia, then into the Amur.

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