(ATLANTA) -- While the world awaits the birth of the youngest heir to the British throne, Zoo Atlanta was on a different kind of baby watch: Panda baby watch. A 15-year-old giant panda named Lun Lun gave birth Monday to a cub, according to zoo spokeswoman Keisha Hines. But two minutes later, as Lun Lun cuddled her cub, something unexpected happen: Lun Lun gave birth to a second panda.
"But then we see a second cub come out. Oh, my God, twins!" Hines told ABC News. "It was sheer panda-monium."
An ultrasound last month determined that Lun Lun was pregnant with a cub, but the zoo didn't see the second one.
The second birth marked the first-ever twin panda births at Zoo Atlanta, Hines said. Zookeepers weren't immediately sure of the genders but the combined weight of the cubs is 8.6 ounces. The newborns are the first giant pandas to be born in the United States in 2013 and the first twins to be born in the country since 1987, according to the zoo.
"The only thing that Zoo Atlanta has over the royal baby right now is that we have twins," Hines joked.
The zoo expects the cubs to make their public debut in November.
Lun Lun and the twins are in good health and she is caring for one of the cubs while staff at the zoo is caring for the other. The zoo says the staff has stepped in to help because Lun Lun has never given birth to twins.
"Obviously, it's a bit nerve-wracking with twins but their weights are good, they look healthy, strong," Zoo Atlanta Deputy Director Dr. Dwight Lawson said. "So far we're off to a really good start with this."
Officials said the newborns' father is 15-year-old Yang Yang, who also fathered Lun Lun's other cubs: Xi Lan, 4, and Po, 2. The zoo has yet to name the cubs, but will follow the Chinese tradition of waiting 100 days to name them.
Zoo Atlanta estimates there are less than 1,600 pandas in the world and these newborns are seen as beacons of hope for the endangered species.
Copyright 2013 ABC News Radio