The Canadian Coast Guard says some kind of oil is leaking from beneath the water near an island in northeastern Newfoundland.
Coast guard spokesman Robert Grant says the first reports of oiled seabirds in the Change Islands and Fogo Island area came in March 31.
Since then, the coast guard and Transport Canada have conducted numerous surveillance flights, with crews spotting small, sporadic slicks during five flights.
Grant says some samples have been collected and sent off to a lab for analysis.
The source of the oil remains a mystery, but Grant says it appears to be coming from an area west of Change Islands.
He says local residents reported seeing up to 400 oiled seabirds at one point.
Liberal environment critic Randy Edmunds says a slick was also spotted off Bacalhao Island, an ecologically sensitive area frequented by seabirds.
Edmunds says he's concerned the slicks may have an impact on the rich fishing grounds in the area.