China says it has arrested seven executives of companies linked to the discharge of industrial waste that polluted a river in southern China with the toxic chemical cadmium. The incident has threatened water supplies for millions of local residents.

The arrests in the Guangxi region come two weeks after official Chinese media first reported contamination and fish deaths in the Liujiang River.

Authorities have released little information about the discharge, which contaminated a 100-kilometer stretch of the river and sparked panic buying of bottled water. But the China Daily newspaper said Tuesday the seven detainees were all executives of chemical companies in the Guangxi region. Cadmium is used to make batteries.

Officials say they are bringing the situation under control. But the China Daily said cadmium levels Tuesday remained 25 times higher near a local hydropower station, below a reservoir where the pollution was first detected.

The newspaper also announced on Tuesday new rules aimed at curbing panic buying and price-gouging. Under the rules, local administrators face punishment if they fail to control pricing spikes when emergency goods become scarce.