The province is investigating after about 30 blue herons were found dead at an oilsands mine in northern Alberta.

Alberta's Energy Regulator (AER) said it will investigate to determine what killed the birds at Syncrude's Mildred Lake facility, about 40 kilometres north of Fort McMurray, Alta.

Bob Curran, a spokesman for the agency, said a Syncrude worker found one heron Wednesday. The bird was alive, but had to be euthanized. After the company searched the area, they found the rest of the birds dead in a run-off pond.

"It would contain mostly rainwater but there was some bitumen in there as well," Curran said.

Systems should keep wildlife out

The area the birds were in is not a tailings pond. Curran said AER is investigating whether the bitumen in the water was naturally occurring or was a result of the plant's operations.

He said the investigation would also look at the systems set up to keep wildlife away from the facility.

"One of the things we are doing is determining whether their deterrent systems were working properly."

Officials at Syncrude could not immediately be reached for comment.

Five years ago, Syncrude was fined $3 million after 1,600 ducks died after landing on a tailings pond at a different facility in 2008. 

Last November, 122 birds were killed after landing in three tailings ponds in the area, including one at Mildred Lake. Curran said in that case, the wildlife deterrents were working properly and severe weather forced the birds to land on the ponds.