LUCHENG - Nearly 9 tonnes of aniline leaked by a chemical plant in north China's Shanxi Province have ended up in the Zhuozhang River, affecting a downstream city in neighboring Hebei Province, local authorities said Sunday.

An initial investigation revealed that a loose drainage valve in the plant, which is owned by the Tianji Coal Chemical Industry Group in the city of Lucheng, was to blame for the leak.

Plant employees spotted aniline leaking from a broken pipe on the morning of December 31, 2012 while conducting a routine check, a company spokesman said.

The Shanxi provincial government said it received a report regarding the leak on Saturday, adding that an emergency response had been initiated to stop the leak and clean up the pollutants.

Another 30 tonnes of spilled aniline have been contained in a nearby disused reservoir, the local emergency response headquarters said.

A statement from the municipal government of Changzhi, which administers Lucheng, said the leak has not resulted in any casualties so far, adding that the river's water quality has been recovering.

Concentrations of aniline in the river have decreased to 2.15 mg per liter from the previous level of 72 mg per liter, according to data from a monitoring station on the river.

However, the concentration should be less than 0.1 mg per liter, according to national standards.

A large amount of dead fish were observed in the upper reaches of the river on Friday evening, according to the emergency water supply headquarters in the city of Handan, located on the river's lower reaches in Hebei.

The Handan municipal government was informed of the accident by authorities in Changzhi on Saturday afternoon and subsequently cut off water supplies for the city, the headquarters said.

Handan resident Geng Huanjie said many people have rushed to supermarkets to buy bottled water after hearing about the incident.

However, water supplies in most parts of downtown Handan have been resumed, as the local government has resorted to an alternate underground water source. Fire engines have also been mobilized to bring water to more of the city's residents.

A local resident surnamed Li said he was able to draw water from his tap Sunday morning, although he added that he is concerned about the quality of the water he was using before the water was cut off, as water was still available for six days after the leak occurred.

"Since the pollutants won't decompose easily, it will likely take weeks to solve the problems caused by the spill," said Zhang Xiaojian, a professor at the environmental school of Tsinghua University.

Aniline, a toxic chemical widely used to manufacture pigments, pharmaceutical industry and other chemicals, can cause serious damage to internal organs, such as the kidneys and liver.

Other rivers have experienced similar contamination in recent years.In 2010, the Songhua River in northeast China's Jilin Province was polluted by chemicals that were swept into the river after floods hit warehouses owned by two chemical companies.

The Longjiang River in south China's Guangxi Zhuang Autonomous Region was polluted with industrial waste in January 2011, killing fish and cutting off water supplies in the city of Liuzhou.

China has witnessed major pollution incidents due to local governments and enterprises' excessive pursuit of economic benefits and neglect of pollution control, said Wang Yinghui, professor with the college of environment at Guangxi University.

Deficiencies in emergency mechanisms to handle environmental incidents at some local governments worsen the pollution problem, Wang added.

Industrial contamination is blamed for China's environmental pollution due to the country's rapid economic growth, said E Xueli, a researcher with the China Disease Prevention and Control Center.

Many large-scale factories have been built along rivers at a small cost and with comparatively little fines for their pollutant discharge or even leakages, he said.

Continuous incidents should sound an alarm to local governments and enterprises, E said, adding that to effectively control public pollution incidents, the government must increase penalties to each violator and close down "repeated offenders."