The U.S. Fish and Wildlife Service says 64 dead walruses were found Monday on a mile-long stretch of Alaska's coastline near the Inupiaq Eskimo village of Point Lay.
Most of the animals were younger than a year old and although the cause of death is still unknown, agency spokeswoman Andrea Medeiros said a stampede is a potential explanation.
"Our thinking is, because of the age of the animals — they were young animals — it's likely that it was caused by a stampede, probably more likely than disease, given the age class," Medeiros said.
She explained that stampedes are often set off when startled walruses rush to the sea. Anything from a polar bear to an airplane could have prompted a stampede.
Alaska Native residents reported seeing an airplane flying near the herd, even though Fish and Wildlife Service guidelines instruct pilots of single-engine planes to stay at least a half-mile from the animals when they're on land or ice.
Medeiros noted that in the past month 30,000 to 40,000 walruses have crowded the beach.
The U.S. Fish and Wildlife Service said it hopes to send a veterinarian to determine what happened to the walruses because no one witnessed a stampede.
The Associated Press contributed to this report.