WASHINGTON (AP) — A female giant panda at the Smithsonian’s National Zoo is a mother for the second time, giving birth to a cub.

The birth late Sunday by Mei Xiang was a surprise after years of failed pregnancies.

Mei Xiang gave birth at 10:46 p.m., the zoo said. The staff can hear the cub making a squawking noise, but has yet to see it because Mei Xiang has built a large nest in her den. Panda cubs are pink and nearly hairless and about the size of a stick of butter.

“I’m cautiously optimistic as we haven’t seen the cub yet, but we know that Mei is a good mother. Like everyone else, I’m glued to the panda cam for my first glimpse of the cub,” Dennis Kelly, the zoo’s director, said in a news release.

The cub is the second born to Mei Xiang and Tian Tian as the result of artificial insemination.

Mei Xiang’s first cub, Tai Shan, was born in 2005.

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