Updated

The first lion cub born in 20 years at Washington’s National Zoo has died after developing pneumonia, devastated officials revealed Friday.

The male cub, born Tuesday, was found dead in the lions' den Thursday evening. Zoo keepers said they found some straw in the cub's lungs, which led to pneumonia.

The zoo said straw bedding for lions and other animals is common throughout zoos and that there was only organic material in the lion's den.

This was the first cub for six-year-old mother Nababiep. Zoo Director Dennis Kelly said the loss was devastating but said it was part of the circle of life.

A statement issued by the zoo said: "On the evening of May 20, the National Zoo’s lion cub died.

"Lion keepers had been closely observing the cub, a male, via camera since his birth early Tuesday morning.

"When keepers noticed the cub was not responding to its mother, they shifted the mother outdoors in order to examine the cub. A veterinary team confirmed his death."

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