A stream winding through a populous area on the outskirts of Buenos Aires has turned crimson red in recent hours, sparking fears of industrial chemical dumping, images shared by residents on social media showed Friday.

Video from a suburb of Argentina’s capital of Buenos Aires shows a bright red waterway. The area has multiple tanneries that use chemicals to treat leather.

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.”