A cadmium pollution stretching 300-km section of a south China river will not result in the cutting of water supplies to a downstream city, according to the local authority.

A spill of toxic cadmium was detected in Liujiang River last Thursday, 11 days after the Jinhe Mining Co Ltd discharged industrial waste into the Longjiang River, a tributary upstream of the Liujiang River. [Xinhua]

The discharges have contaminated the Longjiang River in the southern region of Guangxi for two weeks, sparking panic buying of bottled water in nearby cities.

"After two weeks of cleanup, the pollution is under control and we are certain it won't affect tap water supplies in Liuzhou city or other downstream areas,"?said Feng Zhennian, an official from local environmental protection department.

Feng, who is also spokesman for an emergency response center set up to handle the incident, made the remark at a press briefing Tuesday afternoon.

"The regional government has launched an overhaul on all heavy metal firms as it hopes to halt pollution discharges," he said.

Lab analysis on Tuesday showed the cadmium concentration levels near Liuzhou's water plant were around two times higher than the official limit of 0.005 milligrams per liter, indicating the pollution was under control, said Feng.

As of 6 a.m. Tuesday, drinking water produced by four major water plants in Liuzhou was up to standard, with cadmium concentrations no higher than 0.00065 milligrams per liter, according to the latest water quality tests.

When pollutants were first detected in the Longjiang River on Jan. 15, however, cadmium concentration near the Lalang Reservoir -- where the pollution first leaked into -- was 80 times higher.

The pollutants have been flowing downstream and threatened water security in Liuzhou, a city with 1.5 million permanent residents in the city proper,

The cause of the pollution is still under investigation, seven chemical plants executives have been detained on suspicion of industrial waste discharges.