Local authorities have sent a notice to a Chinese heating company that it will be fined for discharging dyed water into the Yellow River during repairs, turning a half-mile section bright red, a state-run newspaper said Tuesday.

A general view of the polluted Lanzhou section of Huanghe River in Lanzhou, capital of northwest China's Gansu province October 22, 2006. A sewerage pipeline released red sullage to the river and the cause of the pollution is under investigation, local media reported. [Newsphoto]

The incident in Lanzhou, capital of the western province of Gansu, occurred Sunday and caused an uproar in the city of 2 million. Environmental protection officials have taken samples and were trying to determine whether the material was toxic.

It was the latest in a series of industrial accidents that have tainted major rivers in China over the last year.

Lanzhou's environmental authority has delivered the notice to the Lanzhou Tanjianzi No. 2 Heat Providing Station, according to the Beijing Youth Daily. It did not give details on the fine.

An employee who answered the telephone at Tanjianzi said she was "not aware" that a notice had been served but said the company was cooperating with environmental officials.

The woman, who refused to give her name because of the sensitivity of the issue, said hot water in boilers was dyed to prevent people from diverting it for their own use.

She said one of the boilers needed to be repaired and that about 1,500 liters (400 gallons) of dyed water in it was flushed out during the work and discharged into the river.

"The dyed material is not poisonous," the employee said. "We went to the Yellow River yesterday and found the water was no longer red."

Telephone calls to the environmental bureau were not answered on Tuesday.

The Yellow River, which flows across northern China, is the source of drinking water to dozens of cities and tens of millions of people. It has thousands of chemical factories located along its banks.

A part of it runs through the heart of Lanzhou, where residents were indignant about Sunday's discharge. Internet users were also upset.

"Financial punishment will not solve the problem," said a bulletin board posting on Sina.com, one of country's biggest news sites. "The company who caused the pollution should be kicked out of the business."

Protecting the environment has taken on new importance for the leadership following a November 2005 chemical spill in the Songhua River in northeastern China which forced the city of Harbin to shut down its water supply for days.

Already, China's major rivers, canals and lakes are badly polluted by industrial, agricultural and household pollution and hundreds of millions of people live without adequate supplies of clean drinking water.

Throughout the country, protests have erupted over complaints by farmers that uncontrolled discharges by factories are ruining crops and poisoning water supplies.