The investigation continues after a spill in a stormwater pond near Coleraine Drive and George Bolton Parkway in Bolton.
A sample was sent for lab testing, which confirmed the substance is oil.
The site has been secured, and cleanup efforts are underway with support from the OPP, Peel Spills, and the Ministry of Environment.
Authorities say there is no immediate risk to public safety.
Anyone with information about the spill is asked to contact Caledon OPP.
