The belugas have been listed as endangered, with an estimated 375 of the animals left in the area.
A report by the National Marine Fisheries Service suggests 18 possible threats to the whales, including disease, whale poaching and unnatural noise in the water from off-shore drilling and pile-driving, the Anchorage Daily News reported Wednesday.
Researchers said oil and gas spills, ocean warming and partially treated sewage discharged into Cook Inlet also may be playing a roll in the beluga whale deaths.
"Certainly oil and gas development and all in-water activities that might introduce pollutants are a concern," biologist Brad Smith told the newspaper.
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