The Department of Environment, Food and Agriculture is asking people not to dump oil down drains after an incident in Douglas.
A number of ducks were contaminated with oil after someone poured it into drains that emptied into a local pond.
The department says it's investigating but can't say if it was an isolated incident or because of long-term improper disposal.
DEFA Minister Clare Barber is urging people to dispose of oil properly and says businesses should ensure waste oil is safely collected and stored.