(CNN) -- Authorities in southwestern China are reopening their investigation into the death of a teenage girl, following violent demonstrations over how it was handled, state-run media reported Tuesday.
"We must put maintaining social harmony and stability on the top of our agenda," said Shi Zongyuan, a provincial party chief, according to the Xinhua news agency.
The rioting started late Saturday afternoon and lasted until early Sunday morning in Weng'an County of Guizhou Province.
Up to 30,000 demonstrators overturned cars and set fires to protest the police investigation, Xinhua reported.
The unrest stemmed from the June 21 death of Li Shu Fan.
Police said the girl killed herself, and they released several suspects, Hong Kong Cable TV, a CNN affiliate, reported.
The state-run China Daily newspaper attributed the rioters' anger to "officials' alleged attempt to cover up a murder case."
Broadcast images showed several overturned cars in front of buildings in flames. The station identified the buildings as a police station and government building. The amateur video images were recorded by bloggers, the station said.
In March, thousands of anti-Chinese demonstrators rioted in the Tibetan capital, Lhasa. Estimates of the death toll ranged from 18 to 140. Rioters looted businesses and burned homes, stores and vehicles. Pro-Tibetan demonstrators also dogged the Olympic torch relay in several cities around the world.