A Wolong Giant Panda Protection and Research Center spokesman said Ying Ying and Su Lin were the second and third captive-bred pregnant pandas released into the area near the facility, China's state-run news agency, Xinhua, reported Thursday.
The mothers-to-be were moved to two separate semi-wild training grounds in the Wolong Nature Reserve, the spokesman said.
In July 2010, the pregnant panda Cao Cao was released into a semi-wild training ground, where she delivered Tao Tao, a male cub. Mother and cub were found to be healthy and had acquired basic skills necessary to survive in the wild, the center's spokesman said. In February, Cao Cao and her cub were transferred to a larger training base.
Based on the success with Cao Cao, researchers said they would release six more pregnant pandas, including Ying Ying and Su Lin, into a semi-wild environment in 2011.