Thursday's blast at the Tianjiayi Chemical plant in the city of Yancheng is China's worst industrial accident in years. Nearly 1,000 area residents have been moved to safety as of Friday as a precaution against leaks and additional explosions, the city government said in a statement posted to its official microblog.
Windows in buildings as far as about 6 kilometers (3 miles) were blown out by the force of the blast.
The city government statement said 3,500 medical workers at 16 hospitals had been mobilized to treat the injured, dozens of whom remain in critical condition.
The cause of the blast remained under investigation.
China experiences frequent industrial accidents despite orders from the central government to improve safety at factories, power plants and mines.
Among the worst accidents was a massive 2015 explosion at a chemical warehouse in the port city of Tianjin that killed 173 people, most of them firefighters and police officers.
In November, at least 22 people were killed and scores of vehicles destroyed in an explosion outside a chemical plant in the northeastern city of Zhangjiakou, which will host competitions in the 2022 Winter Olympics.