CALGARY, Alberta, Dec. 9 (UPI) -- The Calgary Zoo has launched an investigation after seven Humbolt penguins drowned.
The penguins were housed in a temporary back holding area when they were discovered dead in a pool at 7:30 a.m. Thursday. The ranged from about 8 months to 7 years old.
"This is devastating news," Jamie Dorgan, director of Animal Care at the zoo, said in a zoo release. "We have launched a full investigation so we can try to understand what happened and prevent further incidents like this from happening again."
Jamie Dorgan, the zoo's director of animals, told CTV Calgary they might have become frightened.
"It seems to be some stressor led to these birds going into some kind of panic and having something occur to make them just so panicked," Dorgan said. "But it's hard to say what would've triggered that."
Humboldt penguins are native to the southern coast of Chile and Peru.
Because of renovations in the penguin enclosure, 22 penguins were placed into two separate holding rooms since Monday.
Zookeepers last checked in on them around 4 p.m. Wednesday.
The birds showed no signs of disease and necropsies confirmed they drowned, the zoo said.
In 2013, three penguins died after a deadly bacterial infection swept through the enclosure. Three other penguins died that year from avian malaria.