Oil-fouled seals, seabirds in Bering Strait puzzle experts ANCHORAGE, Alaska (Reuters) - Seals and seabirds in Alaska waters near the Bering Strait have been showing up contaminated with oil from an unknown source, and marine experts were headed to the region to investigate the mystery, federal and state officials said on Friday. Sightings of oiled birds and marine mammals over the past two months have raised "red flags" among state and federal agencies that oversee wildlife and environmental conditions in the region, said U.S. Coast Guard spokesman David Mosley. The precise scope of oil contamination has yet to be quantified, but authorities have so far confirmed two cases of oil-fouled seals harvested by native Alaska hunters and an unspecified number of murres, marine birds common to Alaska waters, he said. Representatives of the Coast Guard and the Alaska Department of Environmental Conservation were on their way on Friday to St. Lawrence Island, in a remote corner of the Bering Strait, to meet with villagers, survey beaches and try to determine the reason for the contamination, he said. No potential oil sources have as yet been identified. While shipping traffic has increased in recent years in Bering Strait and Arctic waters, no recent marine accidents have been reported, and a Coast Guard crew flying over the area on Thursday found no marine pollution, Mosley said. Oil samples from the harvested seals and from one bird were being analyzed by Alaska environmental officials, he added. Also participating in the investigation are experts from the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration, Mosley said. The sightings date back to early September, when a hunter found an oil-fouled seal. The most recent was on Wednesday, when three oiled murres were spotted swimming in the water, he said. So far none of the oiled wildlife belong to species listed as threatened or endangered, state officials said. But the Bering Strait provides vital habitat for numerous protected species, including Steller sea lions and several types of whales. St. Lawrence Island lies just south of the narrow strait that separates Alaska from Russia and is 60 miles from the Siberian mainland.