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.
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"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.