A turquoise lake in Siberia where people have been taking selfies is actually a power plant’s ash dump.

The lake, nicknamed the “Novosibirsk Maldives” because of how tropical it looks, has provided the perfect backdrop to people’s Instagram posts.

But the reason for its colour is less appealing – calcium salts and other metal oxides from the plant.

Responding to the selfies, the Russian power company that runs the plant urged people not to go near the water.

But its stern warning seems to have only made people even more determined to visit.

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Joking about the water being toxic, one user posted a photo of herself reclining on the banks of the CHP-5 ash dump with the caption: “It’s not Chernobyl, of course, but it’s still dangerous!”

Another, tagging the power plant, posted a photo of himself relaxing in a unicorn inflatable while wearing a balaclava.

He wrote, tongue firmly in cheek: “It’s not dangerous to swim here. The next morning, my legs turned slightly red and itched for two days, but then everything went. But what wouldn’t you do for the sake of such pictures?”

He then added that “the water tastes a little sour”.

Leo Alexey, who has set up an Instagram page dedicated to the ash dump selfies, told BBC News that he has already visited the lake four times.

But – naturally – he didn’t go in the water, he just “stood next to” it and “watched”, adding: “It is not advisable to touch the water. It may cause allergies.”

Siberian Generating Company (SGK), which runs the coal plant, wrote on the Russian social network VKontakte in June: “DO NOT swim in the ash dump.”

“The water is highly alkaline,” the company said. “This is because calcium salts and other metal oxides are dissolved in it. Skin contact with such water may cause an allergic reaction!”

It also said that people could get stuck in the ash at the bottom of the water and not be able to get themselves out.

“THEREFORE, WE ARE ASKING – DON’T GET INTO THE ASH DUMP IN THE PURSUIT OF A SELFIE!” SGK added, in all-caps.

The plant also insisted the ash dump was “NOT poisonous”, and that its radioactivity levels had been checked by independent investigators.