Bolivia has sent a group of experts to the southern province of Tarija to investigate after 35 condors were found dead in recent days.
Officials say they fear the animals - 17 males and 18 females - may have died from poisoning.
The Andean condor (Vultur gryphus) is one of the largest flying birds with a wingspan of up to 3.2m (10.5ft).
In December, it had its threat level raised to "vulnerable" from "near threatened".
The International Union for Conservation of Nature updated the Andean condor's status in its annual update to its Red List, which assesses the survival prospects of animals, fungi and plant.
Andean condors are scavengers and primarily eat carrion - decayed flesh of dead animals - and the fear is that they may have eaten poisoned carcasses.
"There's a dead goat in the area and three dogs have also died, so it's likely that poison is to blame," the deputy minister of the environment, Magín Herrera, said.
The governor of Tarija, Adrián Oliva, said that farmers and locals lived in harmony with the condors, implying that they would not have poisoned the birds on purpose.
A team of ornithologists, veterinarians and lawyers will investigate further.