They alleged that a high-ranking official's son was behind the crime.
During the riots, police and government buildings were set on fire. At least one person died and up to 150 others were injured in clashes with police, the Hong Kong-based Information Centre for Human Rights and Democracy said.
Nearly 200 people were arrested.
Parts of the town were returning to normal on Tuesday, with residents shopping and walking around.
Shi Zongyuan, Wengan's Communist Party secretary, visited the area to stress "the importance of social stability", Xinhua said.