About 20 people attacked a government building in a Tibetan area in western China after a man accused of supporting separatism escaped from police custody, a state news agency reported Sunday. Zhaxi Sangwu of Qinghai province had been under investigation for advocating Tibetan independence when he left a police station in Gyala township Saturday, prompting a manhunt, the official Xinhua News Agency said. Xinhua cited authorities from the Tibetan prefecture of Golog as saying the man fled after asking to go to the toilet and remained at large. It cited a witness as saying he was seen swimming in the Yellow River, but police could only find the man's clothes by the river. Officials who answered calls at the local public security bureau and the government said they had heard nothing about the incident. Xinhua's report gave no reason for or details of the violence that resulted.