Some locals were a little concerned this arvo after spotting a bright green/lime coloured substance in the Yarra River near Flinders Street Station.
According to The Herald Sun the liquid has now been cleared and EPA officers are testing the water.
The liquid ran for 15m along the water by the Flinders Street Station entrance near the Evan Walker Bridge.
Image: The Herald Sun
The Herald Sun reported the matter and said the EPA is investigating the unknown substance.
Some locals have taken to social media to suggest the green colour is from a dye used to test leaks in the drainage system.
Do you know what it could be? Tell us in the comments!