SAN DIEGO -- San Diego Zoo officials signed off Thursday on a new panda loan agreement with China to keep the beloved animals in Balboa Park for at least five more years.

San Diego officials and representatives from China marked the agreement at a morning ceremony at the San Diego Zoo.

"The loan agreement between the San Diego Zoo and the China Wildlife Conservation Association symbolizes the ongoing collaboration between conservationists in China and San Diego," said Zhang Yun, consul general of the People's Republic of China in Los Angeles.

"This will be helpful to strengthen the relationship between China and the United States and to promote mutual understanding and friendship between our two people," he said.

The five-year agreement allows the zoo's adult giant pandas -- Bai Yun and Gao Gao -- to stay in San Diego. Pandas born at the zoo will remain there until they are 4 years old.

Most of the $500,000 annual fee paid by the zoo will go to rebuilding the China Conservation and Research Center for the Giant Panda at the Wolong National Nature Reserve, which was damaged during a massive earthquake in the Spring.

"The May 12 earthquake that struck Wenchuan County in Sichuan Province brought major impacts to the Wolong China Conservation and Research Center, which is located near the epicenter," said Zhou Xiaoping, the center's deputy director of research.

"The giant panda enclosures at the Hetaoping Base were severely damaged, and the staff's living quarters were completely destroyed," he said. "The panda habitat has also received various degrees of damage."

The San Diego Zoo has raised $375,000 so far toward an initial rebuilding effort.

The zoo currently pays $1 million a year for adult pandas and $500,000 annually for each cub born under an agreement that is 12 years old and about to expire. The zoo is currently home to two adult pandas and two panda cubs.

Pandas are an endangered species. Four pandas have been born at the San Diego Zoo since 1999.

The first giant panda born in North America to survive into adulthood was born at the San Diego Zoo in 1999. She was named Hua Mei. Since then, three more panda cubs have been born at the San Diego Zoo.

Hua Mei's mother, Bai Yun, gave birth to all four cubs born at the zoo. Hua Bai Yun was artificially inseminated with sperm from Hua Mei's father, Shi Shi, who consistently displayed a complete lack of interest in procreating. He has since been returned to China, where he died of old age.

Bai Yun's other three offspring were fathered by Gao Gao. Both Bai Yun and Gao Gao continue to live at the zoo, along with two of their offspring, Su Lin and Zhen Zhen.

Hua Mei was relocated to China in 2004 and has since given birth to three sets of twins. Bai Yun and Gao Gao's third offspring, Shi Shi, was also relocated to China.