The Champassak Provincial Department of Agriculture and Environment reported on May 4, 2026, that technical teams conducted field inspections after reports surfaced of dead fish floating along the riverbanks starting as early as April 28.
Key observations from the onsite inspection pointed out that the river water appeared turbid and emitted a strong foul odor due to decomposing fish.
The affected area is primarily agricultural with no industrial factories or large-scale commercial activities nearby.
Field tests conducted by specialists using basic water quality meters revealed alarming chemical imbalances. The pH levels recorded at the three locations ranged from 10.16 to 11.30. Typical healthy river water maintains a pH between 5.0 and 9.0.

Experts suggest such high alkalinity (alkaline spike) could be caused by concentrated chemical contaminants such as sodium hydroxide (caustic soda), calcium hydroxide (lime), or sodium carbonate.
While water temperatures were high (31°C to 35°C) and oxygen levels varied, they were not deemed the primary cause of the mass mortality.
Official Safety Measures
Due to the significant risks to human and animal health, the Sanasomboun District Administration has mandating the immediate cessation of water use, recommending residents to stop using Xedon River water for bathing, washing, or agricultural purposes.
It is strictly forbidden to collect or eat dead fish or any other aquatic animals from the river.
Local authorities and village heads are instructed to monitor the situation closely until the water quality returns to safe levels.
Next Steps
The Provincial Department of Agriculture and Environment is currently collaborating with the Department of Livestock and Fisheries and central laboratory facilities. Additional samples of water and fish tissue are being sent for advanced laboratory analysis to pinpoint the exact chemical source of the contamination.
Authorities urge the public to remain vigilant and adhere to the restrictions until a formal "all-clear" is issued.