A police spokesman Thomas Doerflein, 44, appeared to have died of natural causes. There was no reason to suspect suicide or foul play,

he said.

Dorflein raised Knut by bottle after the cub and his twin brother were rejected by their mother when they were just days old.

Knut weighed a tiny 810 grams at birth, and there were real fears he would die, as his brother did after just four days.

But the bear, who turns two in December, thrived and went on to become the star attraction of the Berlin Zoo, generating millions of euros in income through merchandizing and admission fees.