MONTREAL (AFP) - A Canadian zoo said on Thursday it has launched an investigation into the mysterious drowning deaths of seven Humboldt penguins.

"This is devastating news," said Mr Jamie Dorgan, the director of animal care at the Calgary zoo in western Canada.

"We have launched a full investigation so we can try to understand what happened and prevent further incidents like this from happening again."

The penguins were found dead in their normal holding area, the zoo said. Its veterinary team performed autopsies on the birds and established drowning as the cause of death.

There were 22 penguins living in the zoo's Humboldt colony, along with three other penguin species.