– It’s the end of an era at the San Diego Zoo; the last two giant pandas will soon leave for China.

In an announcement Monday, zoo officials said the pandas, Bai Yun, 27 — a fixture at the zoo for 23 years — and her son, Xiao Liwu, 6, must leave San Diego because a multiyear agreement with the Chinese to keep them here has ended. Zoo officials say sending the pandas back was always planned for April and was not prompted by any sudden request from the Chinese government.

The pandas have had a consistent presence at the zoo since 1996. The last day they can be viewed by the public is April 27.

It is unknown if or when new pandas might inhabit the zoo again.

“We have high hopes for pandas returning, but I don’t know that we have any set date when they might return,” said Shawn Dixon, the zoo’s chief operating officer.

There are still pandas at Smithsonian’s National Zoo in Washington, D.C., Zoo Atlanta and the Memphis Zoo.

In the two decades since the first pandas arrived, the animals have become intertwined with the image of San Diego. Their images grace T-shirts and postcards promoting the region, and they even had a starring role in the 2004 “Anchorman” movie. In the film, San Diego news anchors had a daily feature — the “Panda Watch” — chronicling the impending birth of a panda.

While the prospect of no new pandas for the indefinite future might alarm panda fans, there is a promising sign: The zoo has no plans to take down the animals’ exhibit, in hopes it will get more pandas. Several zoo officials are planning to go to China in the coming months to have in-person negotiations with leaders of the nation’s panda program.

“We know our community is going to be sad when they hear this, but it’s a time for celebration,” Dixon said. “They are going home to their home country. It truly is a celebration of all the work we have done.”

The San Diego panda program has been successful by most measures, producing six cubs and developing techniques now used around the world to keep young pandas alive.

When pandas first came to the zoo in 1996, the International Union for Conservation of Nature had listed the species as endangered. Twenty years later, pandas were downgraded to “vulnerable.”

Two decades ago, the wild population of pandas was estimated to be fewer than 1,000. As of the latest count in 2014, there were 1,864 pandas living in the wild, according to the World Wildlife Fund.

Another panda at the zoo, 28-year-old Gao Gao, returned to China in October.