Kuzya, Borya and Ilona are three of the five tiger cubs found in the Far-Eastern taiga some two years ago. The cubs were taken to a special rehabilitation centre and later released into the wild. All the tigers are tagged with tracking devices.
Borya and Ilona are staying in the Amur Region, while Kuzya crossed into China in early October.
"The tiger is doing well and is also hunting boars," the official said adding that Kuzya is expected to return to Russia when the Amur River, which forms a border with northeastern China, gets covered with ice.
When the tigers leave their hunting areas, environmentalists will examine them to get information on the condition and diet of the rare felines, the official said.
The Siberian tiger, also known as Amur tiger, is on the Red List of Threatened Species. In 2010, Russia launched a national strategy to protect the Siberian tiger, the largest of the five tiger species. According to World Wildlife Fund, some 450 Siberian tigers left on the planet.