The National Zoo said Monday that, based on the results of genetic testing, its 6-week-old giant panda cub is male.

“Outwardly, male and female cubs appear similar at birth, so a genetic test was the most accurate way to determine the cub’s sex,” the zoo said in a statement. “During the cub’s first veterinary exam Sept. 19 … veterinarians obtained a swab from his cheek for DNA analysis.”

Veterinarians said the cub appears to be healthy and strong.

The cub weighs 3.6 pounds, measures 14 inches “from nose to tail tip,” and is 12.5 inches around. The cub was born Aug. 21, giving Washington its first giant panda cub in five years.

Zoo officials said they expect to name in the panda in a few weeks.

The cub’s mother, Mei Xiang, 22, is the oldest giant panda in the United States and the second-oldest known in the world to give birth. At that age, Mei had less than a 1 percent chance of having a cub, the zoo said.

She was also the first giant panda in the United States to give birth after the use of frozen semen, the zoo said. The cub’s father, Tian Tian, is 23.

The zoo is open, but with virus safety restrictions. The panda house at the David M. Rubenstein Family Giant Panda Habitat is closed to provide quiet for Mei Xiang and her cub.

The Asia Trail area, which includes the panda viewing area, is temporarily closed for sidewalk repaving.

Mei Xiang has given birth to three other surviving offspring: Tai Shan and Bei Bei, both males, and Bao Bao, a female.

Tai Shan was born July 9, 2005, and was moved to China in February 2010. Bao Bao was born Aug. 23, 2013, and was moved to China in February 2017. Bei Bei was born Aug. 22, 2015, and was moved to China last November.

By agreement, all cubs born at the National Zoo are moved to China when they are 4 years old.

An earlier version of this story misidentified the sex of two giant pandas born in recent years at the National Zoo. Bao Bao is female. Bei Bei is male.