A chemical fiber factory in northwest China has been found to be the source that polluted a 30-kilometer section of upper Yellow River which turned white like milk, local environmental protection authorities said Sunday.

The Lanzhou New Western Vinylon Co. Ltd., located west of downtown Lanzhou, capital of Gansu Province, discharged concentrated waste from production of calcium carbide, a chemical compound obtained by heating pulverized limestone or quicklime, according to a spokesman with Lanzhou Environmental Protection Bureau.

Sample tests showed that the polluting contents of the waste would not affect much the water quality of the Yellow River, the country's second longest, said the spokesman.

"The company will be issued a fine soon, and it has been ordered to take measures to stop pollution," said the spokesman.

A 30-km stretch of the Yellow River near Lanzhou turned white due to pollution Friday morning, which threatened drinking water of about 2.3 million people in Lanzhou as the polluted section neared its tap water sources in the river.

The water color returned normal Friday afternoon.

This is the fourth pollution to hit the Lanzhou section of the Yellow River in about two months.

The stretch turned red on October 22 and November 21 after a heating supply station discharged waste into the river.

Early this month, a paper-making factory dumped waste into a branch of the river near Lanzhou, causing river water become red again.

The 5,464-km Yellow River originates in the Qinghai-Tibet plateau on the "roof of the world" and winds its way eastward before flowing into the Bohai Sea in eastern Shandong Province.

(Xinhua News Agency December 25, 2006)