The Alberta Energy Regulator (AER) said on May 14 it was monitoring the situation after 27 waterfowl were found dead at one of Suncor Energy Inc.'s oilsands tailings ponds.

The company informed the regulator on May 13 that the birds were found at its Syncrude Mildred Lake Settling Basin, AER said in a post on its website.

The deceased birds at Syncrude included seven Grebes, with another five of the endangered bird species being found at the Millennium Mine site tailings pond at Suncor Base Plant.

The Western Grebe, facing the danger of becoming extinct, is listed as "special concern" in Canada and as "threatened" in Alberta.

Suncor did not immediately respond to Reuters request for a comment.

In April, 32 waterfowl were found dead at Suncor's tailings pond on its Base Mine Site.

Tailings — a toxic mix of water, clay, sand, residual bitumen and trace metals — are a byproduct of extracting bitumen from mined oil sands and are stored in huge engineered ponds.

Separately, Canada's federal environment ministry has opened a formal investigation into a months-long tailings leak at Imperial Oil Ltd.'s Kearl oil sands mine in northern Alberta, signaling a potential prosecution.