Police in southern Vietnam recently caught a ceramic tile factory dumping industrial waste into the Thi Vai River, the Vietnam News Agency reported.
Pak Vietnam, a local company that manufactures and sells construction materials, was caught pumping black putrid sewage into a storm drain.
According to reports from VNA, the untreated waste flowed through a drainage ditch into a nearby industrial park before settling in a segment of the Thi Vai River in Dong Nai Province.
A company representative said the sludge came from a coal gasification boiler that broke down several days before police made their discovery.
Investigators have collected samples of the sludge and ordered the factory to halt its dumping at once.
The Thi Vai River became the subject of Vietnam's first major environmental investigation in 2009 when Taiwanese MSG manufacturer Vedan Viet Nam confessed to having piped untreated wastewater into the river for years.
The company's intransigence led to a national boycott of its products.
Even after being forced to pay a US$6 million fine, Vedan was caught again in 2015.
Industrial waste discharges became a serious problem for Vietnam after the country witnessed massive fish deaths along more than 200 kilometers of the central coastline in early April.
Taiwanese steel plant Formosa was held responsible for the disaster as authorities found the firm had discharged a cocktail of toxic chemicals into the sea through an illegal drainage pipe.
Authorities say it's now safe to swim off the coast of the four provinces affected by the disaster, but the integrity of seafood caught within 20 nautical miles (37 kilometers) off the coast remains unclear.Vnexpress