Thousands of geese carcasses have been found in the eastern Idaho area over the weekend.
The birds appeared to have succumbed to avian cholera, according to a statement on the website of Idaho's Fish and Game Department.
Officials are now trying to quickly collect the carcasses for testing.
"The migratory birds were on the return leg of their migration from the southwestern United States and Mexico, to their breeding grounds on the northern coast of Alaska," Steve Smith, a regional supervisor, said on the website of Idaho's Fish and Game Department.
The geese were found near Dubois, Terreton and Roberts -- all in the eastern part of the state.
Avian Cholera does not pose a threat to humans, according to U.S. health officials.