Police have arrested a key suspect in connection with the June 28 unrest in which government buildings were torched in southwest China's Guizhou Province.

Xiong Jiaoxun, a local of Weng'an County in Guizhou, was arrested in the early hours on Monday in a village in Haikou, capital of Hainan Province, the Hainan Public Security Department said on Wednesday.

The department said they began to search for the man on Friday after receiving a class-A wanted order for Xiong by the Ministry of Public Security.

Controversy over the cause of death of teenager Li Shufen whose body was recovered from a river on June 22, sparked off a massive protest and riot in the Weng'an county seat. Office buildings of the county government and public security bureau were torched. Dozens of government vehicles were smashed.

The dead girl was a student at the No. 3 Middle School in Weng'an.

Her relatives suspected she was raped and killed, but a third postmortem after the unrest concluded she had drowned.

Authorities found that gangs in the area had participated in the unrest.