Lao authorities have concluded that wastewater released from a cassava starch factory in Salavanh province caused the recent mass fish deaths along the Xe Don River.
In a video published on the Lao National Radio Facebook page, Chitthamom Ounsida, Deputy Director General of the Department of Environment, announced the findings. Inspections were conducted between 23 April and 5 May along affected sections of the Xe Don River, where local communities had reported hundreds of dead fish.
Investigators found that the Khounmeexay Khongsedone Cassava Starch Factory had illegally released wastewater from its treatment ponds directly into the Xe Don River system.
Authorities said the discharge caused dissolved oxygen levels to fall below national environmental standards, depriving fish of oxygen and causing them to suffocate and die.
Around 460 kilograms of dead fish were collected across several villages in Khongxedon district after residents first reported floating carcasses and foul-smelling water on 23 April.
Officials said rainfall and rising river levels in late April likely carried decomposed carcasses further downstream into Sanasomboun district, Champasak province, where additional fish deaths were recorded between 28 April and 3 May.
Water Testing Results
Earlier water tests on 2 May in Champasak found unusually high pH levels ranging from 10.16 to 11.3, raising concerns over possible industrial contamination.
Later on, the environment department conducted more water quality measurements from 2 to 5 May across 11 monitoring points in Salavanh and Champasak showed that pH, dissolved oxygen, conductivity, and temperature levels had since returned to within national standards, though some dead fish were still found in certain areas.
The authorities have ordered the factory to suspend operations while legal and environmental action proceeds under Laos’ environmental protection regulations.
The government also said the factory owner will be required to take responsibility for environmental restoration and address damages caused by the pollution.
Meanwhile, local authorities continue advising residents not to consume dead fish found in the river and to avoid using river water for household activities or livestock until conditions fully stabilise.


