HARBIN, Nov 24: A toxic slick of polluted river water reached the outskirts of one of China’s biggest cities on Thursday, nearly two weeks after an explosion at a petrochemical plant upstream.

China said the blast had caused major pollution, spilling benzene compounds into the Songhua River from which Harbin, capital of the northeastern province of Heilongjiang, draws its drinking water. Harbin is home to nine million people, including three million urban residents.

Local officials warned residents to be on the lookout for symptoms of benzene poisoning, which in heavy doses can cause anaemia and other blood disorders, as well as kidney and liver damage.

In a sign of how the spill has jarred national nerves about widespread pollution, Prime Minister Wen Jiabao issued instructions demanding safe drinking water be ensured.

In Heilongjiang, Governor Zhang Zuoji ordered hospitals to brace for possible cases of poisoning and promised to drink the first glass of water from city taps once the pollution passes.

According to initial estimates, the explosion resulted in 100 tons of benzene and related products being released into the water, deputy head of the State Environmental Protection Administration, Zhang Lijun, told a news conference.

A provincial government spokesman said the 80-km stretch of pollution passed Harbin’s water supply inlet early on Thursday and would flow beyond the city on Saturday.

Water supplies could resume partially as early as Sunday, Xinhua said. Harbin’s mayor, Shi Zhongxin, said the water would at first be unsuitable for drinking.

Residents’ reactions ranged from stoic acceptance to anxiety, but there were few signs of panic in Harbin, where most residents continued to work and shops and restaurants remained open.

“It’s worrying, because it may not have a strong smell or colour, so you can’t tell when it’s gone,” said Hong Shan, a retired official exercising beside the river. “It’s up to the government to keep us informed. We can’t tell ourselves.”

Farmers in surrounding areas mostly said they draw water from wells, and so were not panicked by the spill. “We’ve stored up enough water to get by, but I don’t know if this pollution can seep into the underground water,” said Gao Erling, from Sifangtai Village near Harbin.

The explosion happened at a chemicals plant in neighbouring Jilin province on Nov 13.

RUSSIAN FEARS: Russia’s environmental protection agency said it was worried the pollution might affect drinking water in its Khabarovsk region, which the Songhua enters several hundred kilometres downstream from Harbin.