The blast occurred at 6:30 pm Thursday night at an industrial park in Sichuan province's Yibin city, according to a statement on the website of the local work safety administration.
The injured had been taken to hospital and were in stable condition, county officials said, adding that the resulting fire had been put out.
Photos on a local news site showed what appeared to be the burned out shell of a building surrounded by rubble.
The company that owns the building where the fire occurred is a chemical manufacturer named Hengda, according to the official Xinhua news service.
China has been rocked by several industrial accidents in recent years.
A septic tank explosion last November destroyed a wide swathe of a light industrial area in Ningbo, just south of Shanghai.
In 2015, giant chemical blasts in a container storage facility killed at least 165 people in the northern port city of Tianjin.
The explosions caused more than $1 billion in damage and sparked widespread anger at a perceived lack of transparency over the accident's causes and its environmental impact.
A government inquiry eventually recommended 123 people be punished. Tianjin's mayor at the time of the accident was sentenced to 12 years in prison for graft in September.
