Picture for representation
Humboldt penguins swim in their pool during the stock take at London Zoo in London Reuters

Zookeepers are guessing that an underwater panic incident in the penguins' colony resulted in the death of seven penguins in Calgary Zoo in Canada. Experts say that something might have triggered frenzy among the penguins which thwarted the efforts of the seven penguins to swim up to surface for air and subsequently caused their death.

It is reported that the authorities are going through CCTV footages but are failing to determine the reason, as the back holding area where the dead penguins were found doesn't come under the surveillance radar.

Zookeepers were baffled after they found seven dead penguins on 8 December in their holding area. Autopsies on all of the birds were carried out by the zoo's veterinary team and it was concluded that the birds died as a result of drowning.

"We have launched a full investigation so we can try to understand what happened and prevent further incidents like this from happening again," said Jamie Dorgan, the director of animal care at the Calgary zoo, according to the Huffington Post.

The holding area houses 22 Humboldt penguins forming one colony. Penguins belong to three other species- kings, gentoos and rockhopper live in the zoo exhibit called the Penguin Plunge.

BBC reported that the 120-acre zoo has witnessed a number of animal deaths under mysterious circumstances. Logan, an American river otter, drowned in the month of February after becoming entangled in a pair of trousers given to it by a zookeeper to play. Also in 2009, a giant capybara was crushed to death in a holding area after a zoo worker mistakenly closed the hydraulic door on it.