This Instagram-ready pond in the heart of the Siberian steppes is more than meets the eye. Budding influencers dubbed it the “Novosibirsk Maldives,” giving rise to a dedicated Instagram account last month with more than 150 posts showing users posing near its eye-catching turquoise waters.

The azure waters are not a natural phenomenon, but the product of an ash dump at a local coal plant. The Siberian Generating Company (SGK) that owns the plant has responded to the social media buzz with a warning to avoid contact with the water at all costs. “Walking in the ash dump is like walking on a military training ground: dangerous and undesired,” the company told Novosibirsk’s ngs.ru news website in early June.

The industrial water gets its captivating color from dissolved calcium and metal oxides. This high mineralization can trigger allergic reactions, SGK warned, while its muddy floor can trap people in the reservoir. “We beg you not to fall into the ash dump in the pursuit of selfies! That’s the biggest danger,” SGK wrote in all caps on its own social media page.

SGK maintains that tests have showed the ash dump at its coal plant outside Novosibirsk is not radioactive. “Our ash dump is not poisonous,” the company said in a social media post last month. “But swimming there is prohibited!”