Xiang Xiang was released into Sichuan's forests in April 2006

Xiang Xiang was released in April 2006 from the Wolong Giant Panda Research Centre and was said to be adjusting well to his new life.

But the five-year-old was found dead in February. Officials said his death was likely due to a fight with wild pandas.

Xiang Xiang's death is a set back for China's efforts to increase the number of giant pandas in the wild.

Giant pandas are one of the world's most endangered species. Only about 1,600 remain in the wild, with another 200 living in captivity.

'Lessons to learn'

Before his release, Xiang Xiang spent three years in a special training compound at the research centre in Sichuan province to prepare him for a natural habitat.

Last year, experts there said he appeared to be integrating into the area's wild panda population.

The lessons we have learnt from what happened to Xiang Xiang will help us adapt and improve the project Zhang Hemin

But he was briefly taken back to the centre in December for treatment after a fight with other pandas.

"We chose Xiang Xiang because we thought that a strong male panda would have a better chance of surviving in the harsh natural environment," Xinhua news agency quoted the reserve's deputy director Li Desheng as saying.

"But the other male pandas clearly saw Xiang Xiang as a threat."

Officials suggested that Xiang Xiang, whose injuries included broken ribs, had fallen from a high place after a fight with other pandas over food or territory.

Zhang Hemin, head of the centre, said that they would continue to release pandas into the wild.

"We are all sad about Xiang Xiang, but it doesn't mean the project has failed," he said.

"The lessons we have learnt from what happened to Xiang Xiang will help us adapt and improve the project."

The delay in reporting Xiang Xiang's death was because of the need for a full investigation, Xinhua quoted officials as saying.