Eight people have been arrested in connection with illegal dumping activities that polluted a local waterway in Southwest China's Yunnan Province, prosecutors said Tuesday.

The Yunnan Provincial People's Procuratorate has approved the eight arrests on charges of polluting the environment, a statement issued by the procuratorate said.

The legal representatives of three ore dressing or mining companies and major managers of the companies were among those arrested, according to the statement.

According to the Xundian County Procuratorate, which is in charge of the case, the companies allegedly dumped wastewater into the waterway directly or via hidden pipes from 2010 to March 2013.

The major pollutant was toxic xanthogenate. Discharging the wastewater, which contained toxic substances and suspended solids, will pollute the water and soil, it said.

Since April 1, media reports have said that pollution caused the water in a 25-km-long waterway located in Dongchuan District of the provincial capital Kunming to turn milky white.

Photos supporting the media claims triggered public anger.