The truck carrying liquefied gas exploded around 4:45pm on the Shenyang-Haikou Expressway south of Shanghai in Zhejiang province, the official Xinhua News Agency said, citing local authorities.
A second explosion followed when the truck fell onto a factory workshop, Xinhua said.
The Wenling city government information office said on its social media account that houses and workshops collapsed and 189 people were treated at six hospitals.
A worker at a nearby restaurant told Xinhua that the blast shattered the windows of her home, but that her mother and brother were unharmed.
The cause of the accident is under investigation, media said.
The government commission responsible for safety production called for the investigation be completed within a certain time, state media reported, without specifying the period.
