About eight tonnes of a toxic chemical spilled into a river near Hangzhou yesterday after a tanker overturned, prompting the authorities to cut off water supplies to people in the area for several hours.
The tanker was carrying the chemical tetrachloroethane when the accident happened in Fuyang in Zhejiang province in the early hours, Xinhua reported.
The chemical is often used to make industrial cleaners and solvents and can damage internal organs and the nervous system if its vapour is inhaled.
Prolonged exposure to the chemical may cause cancer, according to the US Environmental Protection Agency.
Water supplies were cut off for about three hours after yesterday's incident.
The accident is the latest in a series of water supply contamination scares in recent weeks.
Other incidents happened in Lanzhou in Gansu province, Wuhan in Hubei and Jingjiang in Jiangsu province.
Fuyang's government said it was told about the accident by the environmental protection department in Hangzhou at 7am yesterday and decided to cut water supplies from noon.
Fishing was also halted along a stretch of the Fuchun River.
Water supplies were resumed after 3pm. The water supply to Hangzhou was not affected, according to Xinhua.
About 26 tonnes of the chemical was spilled from the truck, but most was contained by barriers and mopped up before it reached the river, according to Hangzhou's environmental protection department.
Qiu Dongdong, a doctor at the Fuyang Traditional Chinese Medicine Hospital, said the accident had a limited impact.
"At home we usually drink bottled water," he said. "In rural areas there are many wells and I heard some people drove more than 10 kilometres to fetch water."
Qiu said that prices had not been raised when he went to buy bottled water from a supermarket after the authorities released details of the accident.
Ma Jun, the head of the Institute of Public and Environmental Affairs, said the frequent water contamination scares over the past few weeks highlighted the need for more public information to be published about the use and transport of toxic chemicals around the country.
"As a factory for the world, China uses a huge amount of these toxic substances," said Ma.
"Without such a reporting system, the public has little idea what risks they're exposed to until a spill occurs."