A stream south of the Argentine capital turned a freakish vermilion this week, prompting concerns about pollution. Officials said it could be the result of “some type of organic dye.”

A canal in Argentina mysteriously turned bright red on Thursday, alarming residents who were woken up by its strong odor. “The smell woke us up. In the daytime, when we looked at this side of the river, it was completely red, all stained,” Avellaneda resident Maria Ducomls told AFP.