Residents of Brazil’s populous São Paulo municipality saw their daytime skies suddenly turn to night on Monday, leaving many wondering whether they were at the doorsteps of an apocalyptic conflict.

Hundreds of netizens took to social media in a desire to get to the bottom of the phenomenon. Some were quick to dish out the apocalypse card, while others compared the eerie appearance of São Paulo to the setting of Mordor, a black, volcanic realm at the center of the fictional world created by writer J.R.R. Tolkien.

However, as it turns out, the Brazilian financial center was not exactly on the verge of hosting Sauron. According to experts, the dark skies were the result of three factors: smoke from forest fires in Bolivia, Paraguay and remote parts of Brazil; a cold front; and the fact that the city sits at an elevation of 2,500 feet.