Yet another explanation

According to [Yin Kim Sean, the secretary of state for the Ministry of Environment], the presence of large amount of excrements in the bottom of the fish cages cause a lack of oxygen and an increase of carbon dioxide concentration. Added to that are the first rains which “warmed up the earth” and increased the water temperature, this would have caused the death of the fishes. (Source)

So it's not poison even though a representative of the SKD winery confirmed that the factory dumped waste in the river. And it's not a naturally occurring chemical reaction in the water, now fifty tons of fish died in warmed excrement. I wonder what explanation tomorrow will bring.