Bolt from the blue: Colorful fireball lights up night sky (VIDEOS)

Is it a bird? Is it a plane? Swedes were left with more questions than answers after the night sky was lit up by a bright blue fireball followed by a loud bang.

Residents in several Swedish towns and cities including Uppsala, Örebro and the capital, Stockholm, reported seeing a mysterious blue flash in the sky late on Monday.

While many were wondering what they had witnessed, Eric Stempels, from the Department of Physics and Astronomy at Uppsala University, was quick to reassure people that this wasn’t the beginning of the end.

“This was something very small that does not pose any threat to us,” Stempels told UNT. The mysterious fireball was, in fact, a bolide – an extremely bright meteor that explodes in Earth’s atmosphere.

"This is something that happens a few times a year," Stempels told The Local. "Because it can happen during the day, when it is cloudy or far from populated areas, these events usually don't get much attention.”

The bolides usually burn up at an altitude of 30-50 kilometers, though Stempels estimates that this one was unusually large, between the size of a “fist and a football” and could have made it as close as 25km to the surface before exploding in an impressive fireball.