Vets were left puzzled after stray dogs covered with bright blue and green fur turned up in two Russian towns hundreds of miles apart within days of each other earlier this month.
In the first case, a pack of dogs with bright blue fur were spotted in Dzerzhinsk – 230 miles east of Moscow.
They had been living close to an abandoned glass factory and chemical plant producing hydrocyanic acid and plexiglass in the city.
It is believed the animals came into contact with the blue dye while wandering close to the factory.
Others suspected it was copper sulphate that had been stored in one of the abandoned warehouses when the industrial unit closed.
The dogs' fur tested positive for the Prussian blue pigment and they are now under supervision at a vet clinic in the neighbouring city of Nizhny Novgorod.
Dmitry Karelkin, lead vet at the Zoozashchita animal hospital, said he believed it was “some kind of chemical” and said the dogs’ excrement had also turned blue.
The second pack, this time with coats dyed a vivid turquoise-green, were found roaming the streets of Podolsk, 20 miles south of the Russian capital.
An animal welfare group reportedly blamed dry paint that may have spilled on the ground, but said it was not toxic and that the dogs were healthy.
Soviet-era factories have long been blamed for polluting the local environment.
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