Steve Oberholtzer, a special agent for the U.S. Fish and Wildlife Service in Anchorage, said 79 walrus carcasses missing their heads and valuable tusks have been found in a 40-mile stretch of shoreline between the towns of Elim and Unalakleet in recent weeks, the Anchorage Daily News reported Wednesday.

Oberholtzer said the number of carcasses is the largest seen by investigators in at least a decade.

Alaska natives are the only U.S. citizens allowed to hunt walruses and they are bound by strict rules that require them to use a "substantial portion" of the animal, including the heart, liver, flippers and some meat.

Oberholtzer said the animals may not have been killed illegally since the heads may have been removed after they died a natural death.

"No one has been charged and we're not speculating wasteful take has occurred," he said. "We're on a fact-finding mission to discover what caused the death of these animals and whether it's legal."