The National Zoo in Washington says its adult female panda has had twins.

The first cub was born Saturday at 5:35 p.m. and the zoo said on Twitter that a second was born at 10:07 p.m. The zoo has said both cubs appear healthy.

If the cubs survive, they would be the 17-year-old panda's third and fourth surviving offspring.

Mei Xiang's first cub, Tai Shan, was born in 2005 and returned to China in 2010. Her second cub, Bao Bao, turns 2-years-old on Sunday and still lives at the zoo.

The zoo's chief veterinarian Don Neiffer said earlier in the day after the first cub was born that a second cub was a possibility.