BOISE, Idaho (AP) — Idaho officials say rodent poison caused some of the 2,000 deaths of migrating snow geese in eastern Idaho found back in March.

The Idaho Department of Fish and Game announced Friday that a handful of the 24 birds sampled in a state lab died by zinc phosphide, commonly found in rodenticides —which is used to farm crops. Biologists initially suspected cholera as the cause of death. Lab results show that cholera may have played a role in the birds' deaths, but it's still not clear how much.

The geese were incinerated to prevent scavengers from eating the sick birds. The department added that the geese were traveling to breeding grounds in Alaska. Roughly 10,000 snow geese are estimated to pass through eastern Idaho on their way north each year.