Take a look at this bright green slime flowing under the streets of Philadelphia. Steven Reitz posted the photo and it went viral.


After the photo made the rounds, the mysterious substance was identified. Although, the green slimy water may look a bit radioactive, it's actually harmless.

Turns out, the Philadelphia Water Department uses a green food dye to help workers identify the cause of sinkholes, cave-ins and other holes in the ground. 

Spokeswoman Laura Copeland told NBC10.com, “Since most of our infrastructure is outside, we use the harmless green dye as it is the most visible and can be seen at the greatest distance."

And there you have it- mystery solved!