Lun Lun, the giant panda at Zoo Atlanta, has given birth to twins.

The twins are her fourth and fifth offspring. She was in labor barely 90 minutes, compared to 36 hours for her first delivery.

Both infants appeared healthy, said Dwight Lawson, the zoo’s deputy director.

The cubs are the first giant pandas to be born in the United States in 2013 and the first twins to be born in the U.S. since 1987, according to Zoo Atlanta.

“This is a success we share with all of our fellow zoological organizations working to understand and protect this iconic species, and we share our joy with our local community and with our colleagues in China,” zoo President and CEO Raymond B. King said in a statement.

“Twins are an entirely new scenario for Lun Lun, Zoo Atlanta and our animal care teams, who will no doubt be extremely busy over the next few months,” King said.

Though giant pandas bear twins in the wild, usually only one cub in the pair will survive because of the difficulty of caring for two, Lawson said.

The zoo hopes to ensure the survival of both infants by switching them regularly, giving them to the mother one at a time.

“It’s tricky,” Lawson said.

Mei Lan, Lun Lun’s firstborn, is in China at the Chengdu Research Base of Giant Panda Breeding. His younger brothers, Xi Lan and Po, are still at Zoo Atlanta.

Visitors can expect to meet the cubs in late fall, the zoo said in a statement. The newborns’ father, Yang Yang, and brothers Xi Lan, 4, and Po, 2, remain on exhibit and will not be housed with Lun Lun or the cubs, the zoo said, noting that separation is normal for giant pandas, which are solitary in the wild.