Zoo conducts autopsy on polar bear star Knut

However, it remained unclear when the results from the examination of Knut, who was found lifeless in the pool in his enclosure on Saturday afternoon, would be published.

"I cannot give you a timeline. We will inform the public when we know what the exact cause was," spokeswoman Claudia Bienek told AFP.

Knut first shot to fame as an ueber-cute cub after being abandoned by his mother and reared by hand. His first public appearance in March 2007 drew around 100 television camera crews from around the world.

But once Knut grew into a strapping adolescent and then adult, animal welfare groups began to worry that he was displaying abnormal behaviour because of all the attention.

He would sway to and fro and even imitate people taking photos by lifting a paw to his face. Hopes that Knut might form a romantic attachment with one of the females were dashed as stories emerged of violent maulings.

Bienek said there were currently no plans to erect a memorial to Knut, adding that a "book of condolence" had already been set up for fans to record their memories of the bear.

"I've been blubbering for days," said one entry of the 1,700 left online.

"I am in complete despair over the death of our polar bear Knut. I cannot put my grief in words," wrote another fan.

(c) 2011 AFP