An oily sheen spotted in the waters of English Bay Monday morning is not recoverable, according to the Department of Fisheries and Oceans.

The sheen, which is being referred to as a “mystery spill,” was reported around 10:45 a.m. It’s so far unclear where it came, what it is, or how much of it spilled into the water.

A Port Metro Vancouver vessel was sent to investigate, and the crew said the sheen appeared light and didn’t give off an odour. The Coast Guard said it’s possible it’s not even petroleum-based.

There’s no evidence marine wildlife or beaches have been affected, and officials believe the sheen will eventually evaporate off the surface of the water through wind and wave action.

The DFO said mystery spills sometimes happen in urban environments, and the one spotted Monday appears fairly minor.