The accident happened around noon at a purification workshop ran by the Hechi Chemical Industrial Group Company in the city of Hechi, Li Chunqi, deputy general manager of the company said.
The injured have been taken to a local hospital for treatment, Li said, adding that their injuries are not life-threatening.
An initial investigation indicated that the blast was caused by a gas leak, state-run Xinhua news agency reported.
The company is a subsidiary of the state-owned China National Chemical Corporation, or ChemChina.