The federal government has opened a criminal investigation into the death of 25 Pacific walrus found on an isolated northwest Alaska beach.

U.S. Fish and Wildlife Service spokeswoman Crystal Leonetti says agency investigators have not returned from the site at Cape Lisburne but that the case is now in the hands of the U.S. Attorney office.

Initial reports last week said the walrus had been shot but the Fish and Wildlife Service refused to speculate on the cause of death until agency personnel had examined the carcasses.

A person connected to an Air Force radar station at Cape Lisburne spotted the animals and notified the agency Wednesday.

The dead animals included 12 pups.

Some walrus were missing heads and tusks. Walrus ivory is prized for jewelry and crafts.