Water supply has been cut for about 60,000 residents in the town, who are relying on bottled water. Five schools also have stopped classes.

The environmental protection authorities were investigating the source of the contamination, Xinhua said.

Meanwhile, in southeastern China's Yunnan Province, police have detained a farmer whose homemade fertilizer contaminated the drinking water of 9,000 people and killed 20 tonnes of fish in a fishery last week, Xinhua said.

The villager, Zhou Shunfu, dumped 120 tonnes of waste residue with phosphor onto his own fields, thinking that it could be used as fertilizer, and wiped out a neighbour's fish farm.

After a string of well-publicised cases of water pollution, China is moving to crack down on industrial polluters. It is debating a draft law to fine the heads of companies that foul water, and contemplating ending tax breaks for polluting exporters [ID:nPEK56374].

But accidents and careless use of chemicals still poses a grave hazard, especially in smaller towns.