Environmental police in Binh Duong Province discovered two pipes from an industrial zone discharging untreated wastewater into the Saigon River.
The stinking sewage laced with oil scum was discovered Wednesday flowing from Dong An No.1 Industrial Zone into a canal that empties into the Saigon River.
Police said the pipes, which were designed for rainwater runoff, were discharging around 1,000 cubic meters a day, on days it's not raining.
Nearby residents said the pipes have been discharging the black water for many years.
The investigators have collected samples of the wastewater for testing. They also checked the wastewater that the zone claimed had been treated but appeared dark and noxious as well.
Hung Thinh Joint Stock Company, which invests in the industrial zone, was asked to explain the problem in a written statement and stop the flow of wastewater at once.