04/26/2013 03:50 EDT | Updated 06/26/2013 05:12 EDT

Source of sporadic oil slicks off northeastern Newfoundland remains a mystery

ST. JOHN'S, N.L. - The coast guard is preparing to deploy a sonar device and a submersible vessel to determine the source of oil leaking from beneath the water near an island in eastern Newfoundland.

Coast guard spokesman Robert Grant said Friday that reports of oiled seabirds and small slicks were first reported March 31 in the Change Islands and Fogo Island area.

Since then, the coast guard has traced the source of the oily substance to an area west of Change Islands, though they have been unable to confirm the sightings of oiled birds.

Grant says the coast guard plans to use a multibeam sonar in the coming days to see what's on the bottom.

As well, there are plans to use a remotely operated miniature submarine to take samples and videotape the ocean floor.

He says the coast guard has encountered this kind of situation before when small fishing boats have sunk, but he says it remains unclear what the oily substance is.