You've heard of a white Christmas, but have you heard of a blue Christmas? (And no, we don't mean the Elvis Presley classic.)

An extraordinarily bizarre event occurred in St. Petersburg, Russia, on Dec. 26: blue snow falling on the city. The freaky weather phenomenon sparked widespread fears that the snow was tainted with some kind of toxic pollutant. So far, no official explanation has been offered for the blue snow, though an investigation is underway, reports ABC News.

The predominant theory among residents seems to be that the blue snow was caused in some way by the recent demolition of the city's chemical-pharmaceutical research institute. Scientists have suggested that the tinted ice could be caused by cobalt, a metallic element, or methylene blue, a substance used in some medical treatments.

Residents were simply forced to attempt to go about their daily lives in spite of their shocking surroundings; shoveling the blue stuff, clearing roads and driveways.

“We cannot guess what has happened and why snow is blue without laboratory results. We have sent the snow to laboratories to check it for toxicity and metals,” said Gulnara Gudulova, press secretary of the Russian ecology watchdog, Rosprirodnadzor.

Interestingly, this isn't the first time that blue snow has fallen on a Russian city. Back in 2015, blue snow also occurred in the Russian city of Chelyabinsk, some 1,500 miles to the east of St Petersburg. The cause of that incident was determined to be blue food coloring used in Easter eggs, which had gotten into the ventilation system of a factory and been spread all over the area.

Needless to say, residents of St. Petersburg should probably avoid getting into any snowball fights or creating any blue snow angels until the cause of the weird event has been determined to be non-toxic.


Mysterious blue snow falls over parts of Russia
No one knows what caused the blue snow in St. Petersberg, but an investigation is underway.