A self-constructed residential building in central China's Hunan Province collapsed on Friday, local authorities said, adding that casualties remain unclear as of now.The incident took place in Wangcheng District in the provincial capital Changsha around noon.A self-constructed residential building in central China's Hunan Province collapsed on Friday, local authorities said, adding that casualties remain unclear as of now.The incident took place in Wangcheng District in the provincial capital Changsha around noon.