"In order to safeguard water safety in the urban districts, the municipal government has decided to provisionally stop supplying water to the public water network," the government of Harbin city, the capital of China's northeastern Heilongjiang province, said in a statement.

The order comes after a November 13 explosion at a petrochemical plant in Jilin city, about 380 kilometers (230 miles) up the Songhua river from Harbin.

The explosion killed at least five people and resulted in the temporary evacuation of tens of thousands of others who were forced to flee a cloud of toxic smoke.

"At present there is no sign of any abnormalities along the Songhua river in the Harbin section, but the environmental protection agency expects that up-river pollution could appear in the coming days," the government said.

Government officials, when contacted by phone, refused to say how many people would be affected by the water stoppage, only saying that the supply would be cut off for four days beginning at 8:00 pm Tuesday.

Harbin is a city of more than eight million people, but only some three million people live in the city's urban districts.

Locals aware of the pending water stoppage began hoarding water and food supplies as early as Sunday, amid government pronouncements to remain calm and "stop listening to rumors," state press reports said.

"City industry and commerce bureaus, police and other departments must strengthen supervision and management of markets and ensure market and social order," the local government statement said.

The government was also forced to quell wild rumors that Harbin was going to be hit by an earthquake, state press said, a reflection of both the panic in the city and the lack of timely information by authorities.

"The talk that Harbin will be hit by an earthquake in the coming days is purely rumor, residents should not worry, there is no need to panic," a Heilongjiang seismological bureau spokesman told a government-run news website.

"There is completely no need to buy up and hoard food items, or set up tents to live outside."

Local supermarkets reported all their bottled water had quickly sold out due to the panic buying, as state press showed pictures of empty shelves and shoppers hoarding water, soft drinks and other potable products.

Government offices, factories, enterprises and institutes such as hospitals and schools were also told to ensure their water storage facilities were full before the stoppage began.

Bath houses and car washing facilities were ordered to close down.

The November 13 blast at the Jilin Petroleum and Chemical Company, which is located on the banks of the Songhua river, was due to a failure by workers to shut a gas valve in a timely manner.

This led to exceedingly high temperatures setting off a series of explosions that levelled two of the plant's fuel towers where the highly flammable gas benzene was being processed, Xinhua news agency said.

Over 60 people were injured in the blast, with 23 still in hospital. After allowing the evacuees to return, the government gave no indication in the state press that the accident may have polluted the water stream.

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