Residents of St. Petersburg, Russia, were startled to see a strange, blue snow blanketing their city last Tuesday.

The cause of the snow's coloration is currently unclear, but locals are concerned that it could indicate the snow has been contaminated with metals and toxins; such as cobalt, a metallic element, and methylene blue, which is used in medical treatments.

Local residents believe that these substances could have been released during the ongoing demolition of a chemical and pharmaceutical research institute in St. Petersburg.

"According to our assumptions, it was brought by the wind from the chemical and pharmaceutical research institute, which they began to demolish on Aptekarsky Avenue," local resident Ekaterina told Russian media outlet Fontanka.

Fontanka released the following video, documenting the snow's bizarre hue.