Dozens of endangered penguins in South Africa were killed last week by a swarm of bees.

More than 60 of the protected birds were found Friday on Boulders Beach, a tourist spot near Cape Town with multiple bee stings. The Southern African Foundation for the Conservation of Coastal Birds said in a statement that it suspected a nest of Cape honey bees was to blame.

Many dead bees were also found on the scene.

At first, investigators thought a predator had caused the deaths, but postmortems revealed bee stings around the eyes of the birds, Katta Ludynia, research manager at the foundation, told NBC .

It was the first known attack of its kind.