Over two tonnes of sulfuric acid flew through the gate of the plant and onto a busy road outside, toppling several motorcycles and injuring at least six people, police said.
The accident took place on Friday when the sulfuric acid was being unloaded from a truck at a plant in Xingning District of the provincial capital Nanning, state-run Xinhua news agency reported.
A one-year-old child sustained serious burns covering 19 per cent of his body, it said.
An initial investigation shows that an improper unloading practice caused the spill, it added.