A trio of three-storey buildings were reduced to their steel frames by the explosion, the Sichuan Daily newspaper said, citing eyewitness accounts.
Windows of nearby buildings were shattered by the explosion at the factory, which is surrounded by a sand and gravel plant, it added.
The plant has three production lines, making 300 tonnes per year (tpy) of benzoic acid, which is used in food preservatives, and 2,000 tpy of 5-nitroisophthalic acid, for medicines and dyes, the regional environmental protection bureau says.
China's breakneck pace of economic growth during the last decade has resulted in a spate of industrial accidents.
In 2015, an explosion in a chemical warehouse in the northern port city of Tianjin killed 165 people. Last year a blast at a petrochemical plant in eastern Shandong province killed eight people and injured nine.