An investigation into the dumping of untreated water in east China's Jiangxi province, which disrupted local water supply, was launched by the Ministry of Environmental Protection (MEP) on Thursday.

According to a MEP statement, on April 3, a chemical plant dumped untreated water containing a "large amount of cadmium, thallium and arsenic" into the Yuan River, contaminating the river and Xiannv Lake, a major water source for Xinyu, an industrial city of 1.1 million people.

As a result, water supply in some areas of Xinyu was cut off.

The MEP identified the incident as a "major environmental emergency." The results of the investigation will be publicly disclosed once it is complete, it said.

The water supply in Xinyu has been back to normal since April 12. The water quality has been tested by the health authority, and was deemed stable and safe.