ANCHORAGE, Alaska — A polar bear at the Alaska Zoo has died.

Officials announced on the zoo website Monday that 19-year-old Lyutyik (LOO-tee-ik) died Sunday.

The beloved animal was generally referred to as Lyu (LOO) or Louie. He was part of the zoo since 2006.

Zoo officials last week said the bear two months ago had become lethargic and was refusing to eat. Caretakers removed him from his usual habitat for monitoring.

After the bear died, an evaluation found a mass around and in one of his kidneys. Zoo officials say the condition often goes undetected in animals that large. A more comprehensive pathology review is planned.

Polar Bears International says some polar bears in captivity have lived to their mid- to late 30s.

The death was first reported by KTUU-television.