Native Alaskan hunters have found two oil-fouled seals in the region, and an unspecified number of contaminated marine birds, known as murres.
A single crested auklet has also been found coated with oil.
There have been no reports of recent marine accidents that could have spilled the oil, and aerial surveillance has so far failed to spot any marine pollution in the waters around St. Lawrence Island, where the oiled wildlife has been found.
Oil samples taken from the seals and one of the birds were being analyzed by Alaskan environment officials.
St. Lawrence Island and its surrounding Bering Strait waters are home to threatened or endangered species such as spectacled and Steller’s eiders.
But none of these species are known to have been affected so far.