BEIJING - Police in southwestern China have ruled out allegations that a government official's son was involved in the rape-murder of a girl that sparked a riot by 30,000 people, state media reported on Wednesday.

The denial by authorities in Guizhou province, reported by the province's Jinqian Online news service, appeared to contradict a state media report a day earlier that police would reopen an investigation into the highly sensitive case.

The death of 17-year-old Li Shufen in Weng'an county triggered a violent outburst on Saturday by 30,000 residents who attacked and burned government and police targets.

The anger was fuelled by local rumours that the son of a top county official was involved in raping and killing the girl and that police had exonerated him. Xinhua news agency on Tuesday cited officials as saying the case would be reopened after they acknowledged public suspicions about the handling of the case.

But Jinqian Online quoted local police official Wang Daixing, who it said had been involved in the forensic investigation, telling a news conference that there had been no rape.

"According to investigations, there was no sexual activity before the death," said Wang.

The report also quoted local party official Luo Yi saying the government official whose son was accused of the crime actually has no relatives in the area and that the girl was with other people at the time of her death.

Police maintain Li committed suicide by jumping in a river.

The incident has embarrassed China's Communist Party rulers, who have been trying to avoid any form of protests in order to showcase the nation as harmonious and stable ahead of the Beijing Olympics in August.

The Hong Kong-based Information Centre for Human Rights and Democracy has said more than 2,000 paramilitary and riot police had been dispatched to the county to squelch the unrest and that at least 300 people had been arrested.

China sees thousands of such outbursts each year as ordinary Chinese, faced with an unresponsive legal system and rampant official corruption, lash out violently at graft and perceived government abuses.