HONG KONG  — Hong Kong welcomed the birth of its first locally born giant pandas on Thursday, with their mother becoming the world’s oldest first-time mother of its kind on record, the theme park that houses them announced.

Ying Ying, the mother, gave birth to the twins — one male and one female — at Ocean Park just a day before she turned 19 years old, the park said in a statement.

She and her partner Le Le are the second pair of pandas gifted by China to Hong Kong since the former British colony returned to China’s rule in 1997.

Pandas are widely considered as the country’s unofficial national mascot and China’s giant panda loan program with overseas zoos has long been known as a tool of Beijing’s soft-power diplomacy.

Ocean Park said in the statement that giant pandas have a “notoriously difficult time reproducing, especially as they age” and panda pregnancy is not readily detectable.

Although Ying Ying started showing symptoms including decreased appetite, increased need for rest time and changes in hormonal levels in late July, her pregnancy was only confirmed on Sunday. On Wednesday, her care team noticed Ying Ying’s labor symptoms and her amniotic fluid broke at night. After over five hours of labor, the babies were safely delivered Thursday morning, the park said.

“Both cubs are currently very fragile and need time to stabilize, especially the female cub who has a lower body temperature, weaker cries, and lower food intake after birth,” the park said. Visitors will have to wait for a few months for their public debut.

Ocean Park Corp. chairman Paulo Pong thanked the local animal care team, as well as experts from mainland China for their partnership and assistance over the years.

“The birth is a true rarity, especially considering Ying Ying is the oldest giant panda on record to have successfully given birth for the first time,” Pong said.

Hong Kong leader John Lee also expressed his gratitude to the central government for gifting the pandas to the financial hub in 2007, saying it showed Beijing’s care and support for the city.

Hong Kong has its own governing and judicial system and China authored a 2020 national security law that has been used to prosecute pro-democracy activists.

In July, Lee announced that Hong Kong would receive a third pair of pandas from China. The pair is expected to arrive this year.

The late first pair, An An and Jia Jia, arrived in 1999. Jia Jia, who died at 38 in 2016, is the world’s oldest-ever panda to have lived in captivity. The average lifespan for a panda in the wild is 18 to 20 years, while in captivity it’s 30 years, according to Guinness World Records.