First there were bright blue stray dogs, then bright green ones. Russia is trying to solve the mystery of these dogs, which appeared in industrial areas hundreds of miles apart.
Seven dogs with blue fur were found roaming near a derelict glass factory in Dzerzhinsk, an industrial city near Nizhny Novgorod, 370km (230 miles) east of Moscow. The pictures went viral after local media reported the strange pack of dogs on 11 February.
The factory had been producing acrylic glass and prussic acid. It is suspected that the dogs rolled around in powdered blue dye at the plant.
On 13 February the dogs were brought to a vets' clinic in Nizhny Novgorod, where blood and faeces samples were taken. Traces of Prussian blue dye were found in their fur.
Russian media report that the dogs appear healthy and are eating well. But there are still concerns that a toxic chemical, such as copper sulphate, might have caused the colour change.
On Thursday several dogs with bright green fur were seen roaming around Podolsk, an industrial town 37km (23 miles) south of Moscow. In this case, according to a Moscow regional minister, the dogs were seen near an abandoned warehouse, where sacks of powdered green paint had been stored.
But some Russians on social media suspect the Podolsk dogs might have been deliberately painted for a sick joke, as the bright blue dogs had impressed so many people earlier.
Vets have been examining the Podolsk dogs too. The cause of their green fur has not been conclusively established. But as in the Dzerzhinsk case, the dogs appear quite healthy and friendly.
Whatever caused the bright-coloured fur, the cases highlight the continuing risk from chemical pollution in Russia, which has many old industrial plants, partly a legacy of communism.
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