The two mammals had been prepared for their release since their birth, according to the China Conservation and Research Center for the Giant Panda.

Efforts were made to avoid unnecessary contact between the pandas and human caretakers, and humans entering the training area were camouflaged with panda costumes and the scent of the animals, the center said.

In late November, experts decided the two giant pandas had acquired relatively strong survival skills for the wild.

Nine captive pandas previously had been released, starting in 2006, and seven of them are still alive.