Chinese authorities are dealing with the second water pollution scare in less than a month, after authorities in eastern China said an acid used in detergents had contaminated a regional water supply.

State media reported Wednesday that officials in Jiangsu province found the chemical phenol in the Yangtze River, which supplies most of the water for China's most populous city, Shanghai.

Residents in nearby Zhenjiang said their tap water had a strange smell on Friday, prompting a run on bottled water. Officials said the pollution did not cause a health threat, and there were reports that the water quality had since returned to normal.

Reports said the contamination may have been caused last week by a leak from a South Korean ship.

The incident comes just weeks after the cancer-causing chemical cadmium was found in the Liujiang River in southern China, threatening water supplies for millions of residents.

Chinese authorities arrested seven executives of chemical companies linked to the discharge, which contaminated a 100-kilometer stretch of the river and also sparked panic buying of bottled water.