Seven penguins mysteriously drowned at Calgary Zoo last week.

The animals drowned in the back holding area of the Penguin Plunge exhibit.

Jamie Dorgan, the zoo's director of animal care, told CBC: "It was very surprising for us to find this group of birds dead.

"Our penguin keeper went up to the building this morning to do her normal routine and unfortunately found one penguin deceased in the pool and was quite shocked to see that multiple penguins were dead in the pool."

The zoo's management is confused, as penguins are aquatic animals and spend most of their time in the water.