CHENGDU, May 18 (Xinhua) -- A pair of two-and-a-half-year-old giant panda twins that were born in Spain returned to China on Saturday.

Pandas "De De" and "A Bao" arrived at the Chengdu Research Base of the Giant Panda Breeding in southwest China's Sichuan Province on Saturday after traveling from a zoo in Spain's capital city of Madrid.

"De De weighs more than 70 kg while A Bao weighs more than 80 kg. Both are in good health," said Cai Zhigang, a member of staff at the base.

The twins will undergo a month-long quarantine process before they make their first public appearance in China, according to the base.

Their mother "Hua Zui Ba," who was sent to Spain from Sichuan, was artificially impregnated and gave birth to them in September 2010. The twins are the first pair of giant pandas to be born overseas from artificial insemination.

The base has established panda breeding programs in collaboration with Japan, the United States, and European countries. The programs intend to increase global understanding of the endangered species' feeding and breeding habits.

According to cooperative agreements between China and Spain, cubs born to pandas that are "on loan" from China belong to China and must be returned after they reach two years of age.

"De De" and "A Bao" are the 10th and 11th giant pandas to have been born overseas and to have returned to China.