As of Tuesday morning, four of the six missing pandas had returned to Wolong and staff are searching for the other two.
"Rescuing the missing pandas and taking care of the others in the center are our top priorities now," said Xiong, adding aftershocks could be felt in Wolong at every few hours.
The eight two-year-old pandas, selected by netizens from 16 candidates born in 2006 in the Wolong center, will be on display at the Beijing Zoo until November, and are expected to attract more than six million tourists from home and abroad during the six-month show.
The zoo has already begun to upgrade its facilities to accommodate the additional animals.
There are about 1,590 pandas living in the wild in China, mostly in Sichuan and the northwestern province of Shaanxi and Gansu. Another 180 have been bred in captivity.
More than 60 pandas at another breeding center in Chengdu were reported safe after the quake. Another eight pandas at a preserve in Ya'an, about an hour's drive west of Chengdu, were safe as well.
The Wolong center is deep in the hills north of Chengdu along a winding, two-lane road that has been partially blocked by landslides.
(Xinhua News Agency May 20, 2008)