TUCSON, Ariz. (CBS4) – If you have lived in Colorado for a while you probably remember the lovable polar bear cubs Klondike and Snow from the Denver Zoo.

The cubs captured many a heart when their mother abandoned them after birth in 1994. The zoo staff raised them, and when they grew up the pair were sent to Sea World in Orlando, Fla. Snow moved to a zoo in Tuscon earlier this year and was found dead in her pen Monday morning.

Denver Zoo staff stayed with Klondike and Snow day and night, concocting special formulas to nourish them. It had been more than 10 years since any zoo had succeeded in hand-raising a polar bear cub.

Snow had a complicated medical history. She had rickets when she was young. In recent years she developed horrible skin allergies. Still, zoo keepers were shocked to find her dead.

A necropsy will determine how she died.