He may look cute and cuddly but Knut, the world’s most famous polar bear cub, stands accused of conspiracy to murder.

As thousands of wellwishers flocked to Berlin Zoo to coo and sigh over his antics, few were aware of the tragedy that unfolded only a cage or two away. Yan Yan, the zoo’s most popular resident until Knut’s arrival, died suddenly aged 22.

A gift from the Chinese leadership to Helmut Kohl, the former German Chancellor, Yan Yan spent much of her time lying on her back chomping at bamboo shoots and was, by all accounts, a happy panda. Heinrich Kloes, the zoo’s chief bear curator, said there that had been no signs of illness.

But something changed on Monday, days after Knut’s introduction to tumultuous crowds, and Yan Yan lay down and died. The cause of death has yet to be determined but already fingers are being pointed at three-month-old Knut.

The mass circulation Bild newspaper does not believe in coincidences. “Panda Yan Yan dies in Berlin Zoo”, said its front-page headline. “Because of Knut?”

Up to 30,000 people a day have been queueing for a glimpse of the cub, who has been bottle-fed by keepers since his mother, a surly ex-East German circus animal, rejected him.

As many visitors were unable to see Knut through the crowds, they moved on to pay their respects to Yan Yan. Flashbulbs popped from dawn to dusk. That, according to Bild, may have been too much for Yan Yan to bear. “She seemed restless and intimidated,” the newspaper said. The verdict: fatal stress induced by Knut, or at least by his fans.

Yan Yan was even more of a rarity than Knut. There are only 1,600 pandas living in the wild. Pressure was piled on Yan Yan from the beginning to conceive as quickly as possible. Her partner, Bao Bao, tried his best, once every six months or so, but they both lost interest after Yan Yan miscarried in 1997. Chinese experts were flown in to inject some hormones but at €15,000 (£10,200) a session, the zoo gave up. Yan Yan’s heart was, in any case, no longer in it.

Her celebrity faded. Knut’s star, however, continues to rise. He is still being staked out by paparazzi and film crews, and charmed fans yesterday by chewing his keeper’s boots.

The zoo sold 2,400 Knut cuddly toys at the weekend and is rushing thousands more into production to restock its souvenir shop and meet orders from Austria and America. Haribo, the German confectioner, plans to add a Knut-shaped design to its range of jelly-bear sweets. “We are reacting to a strong demand from parents and children,” said Marco Alfter, a Haribo spokesman. The German version of the internet auction site eBay had more than 200 Knut items for sale yesterday.

The zoo has copyrighted the Knut name and is planning a range of further products, promising that profits will go towards animal conservation. The marketing men, however, see one problem with the appeal of their cuddly new star — he is growing fast. Knut currently weighs 9kg (20lb) but a fully grown polar bear can top the scales at 600kg.

Times Recommends

• Rio Tinto four held as China prepares case
• Diplomats must keep heads down and trousers up
• When in Rome should one make like Berlusconi?