The incident happened near Hebei Shenghua Chemical Co. in Zhangjiakou, a city some 200 kilometres (124 miles) northwest of Beijing that will host the 2022 Winter Olympics.
The fire also burned 50 large and small trucks, the local propaganda department said on its Weibo social media account.
The injured were taken to hospital for treatment following the blast, which occurred at 00:41 am, according to the statement.
The charred and smoking remains of trucks and cars were scattered on a road as firefighters worked at the scene, according to photos posted on Twitter by state broadcaster CGTN.
The statement did not say whether the factory was affected by the blast or whether it took place on a road.
“On-site search and rescue work and investigation of the cause of the accident are still under way,” the propaganda department said.
Zhangjiakou will host the Olympic alpine skiing events at the 2022 Winter Games, which Beijing is organising.
It was not immediately clear if the explosion was near the site.
Road and industrial accidents are common in China.
A blast at a chemical plant in southwest Sichuan province left 19 dead and 12 injured in July. The company had undertaken illegal construction that had not passed safety checks, according to local authorities.
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.
China has also also experienced its share of horrific road crashes, with traffic regulations often flouted or unenforced.
Two cars ploughed into crowds in two separate incidents in recent days: Five children were killed when a driver deliberately rammed into students crossing a road in northeast China last week and seven people died when another car hit people on a sidewalk in the southwest on Tuesday.
An out-of-control truck ploughed into a 31-car lineup in northwest Gansu province earlier this month, killing 15 people and injuring 44.
In November last year, a highway pile-up involving at least 30 cars killed 18 people in eastern Anhui province.