Officials inspected fish in the Lang River near Pha Mon Cave, Mae Hong Son Province, after numerous abnormal fish deaths were found. A warning was issued advising against consuming the fish.
On 10 March 2026, Mr. Weeraphong Rattanasri, District Chief of Pang Mapha, ordered security forces, Mae Hong Son provincial fisheries officials, Pang Mapha public health officers, Singhanat Task Force soldiers, Pai River Wildlife Sanctuary staff, and Pang Mapha Forest Protection Unit to investigate the unexplained fish deaths in Phamon Stream and Lang River near Pha Mon Cave, Sop Pong Subdistrict, Pang Mapha District, Mae Hong Son Province. Officials collected water samples and fish carcasses from the area to determine the cause of death.
Most of the dead fish were large stone bass living within Pha Mon Cave where the Lang River passes through. Many fish have died progressively since 27 February 2026 and continue to this day.
Regarding a dead pigeon found near the Lang River, officials remain skeptical that the bird died from drinking the river water, as only a single bird was found. It is suspected the bird may have had a prior illness and died after drinking the water, leading locals who saw the fish carcasses to mistakenly believe the bird died from drinking Lang River water like the fish.
The investigation results are expected to be available next week. Meanwhile, residents in the area have been strictly prohibited from consuming fish from the river.
