A 15-year-old giant panda, Lun Lun, gave birth Monday to twin cubs at Zoo Atlanta, according to the Chengdu Research Base for Giant Panda Breeding in Sichuan province, Chinanews.com reported.

A pair of giant panda twins born to Lun Lun are pictured at Zoo Atlanta in Atlanta in this July 15, 2013 picture provided by Zoo Atlanta. A giant panda at the Atlanta zoo delivered an extra bundle of joy on Monday when she gave birth to twins, an apparent surprise to zoo officials who had been excitedly anticipating the birth of a single cub. [Photo/Agencies]

Zoo spokeswoman Keisha Hines said it's the fourth time Lun Lun gave birth and her first set of twin cubs.

The newborns are the first giant pandas to be born in the US in 2013 and the first twins to be born in the country since 1987, according to Hines.

The baby pandas are expected to debut later this year.

Lun Lun was confirmed pregnant on June 30. Giant panda Yang Yang is the cubs’ father.

They have three other offspring together: Mei Lan, Xi Lan and A Bao (Po), born in 2007, 2009, 2011.