Photos circulating on social media showed plumes of smoke coming out from the remains of the building.
In a statement quoted by Reuters, the authorities in Jiang'an county said the blast happened at a chemical plant run by Yibin Hengda Technology.
Rescue workers try to put out a fire after an explosion at a chemical plant inside an industrial park in Yibin, Sichuan province, China July 12, 2018.
The country has introduced measures to improve industrial safety over the past year, following incidents at coal mines and chemical plants.
Authorities have begun an investigation, the news agency said. "It took a couple dozen firefighter trucks to put out the fire".
The company that owns the building where the fire occurred is a chemical manufacturer named Hengda, according to the official Xinhua news service. The fire broke out in the early evening while there was still daylight, and it was under control by around 11:30 p.m. according to reports.
A trio of three-storey buildings were reduced to their steel frames by the explosion, the Sichuan Daily newspaper said, citing witness accounts.
The note notable example in recent years being the 2015 blast that rocked the city of Tianjin, and resulted in the deaths of 165 people in the area near the port storage facility.
Last year, an explosion at a petrochemical plant in eastern Shandong province killed eight people and injured nine.