A huge explosion rocked a chemical plant in eastern China on Thursday, killing at least six people and injuring dozens as it knocked down factory buildings and sent a huge plume of smoke skyward, officials and state media said.

The blast occurred at around 2:50pm (0650 GMT) at a facility run by Tianjiayi Chemical in Yancheng, Jiangsu province, city officials said on their official Twitter-like Weibo account.

It is the latest industrial incident to rock China in recent years.

Around the time of the explosion, China's earthquake administration reported a 2.2-magnitude tremor in Lianyungang, a city near the Yancheng blast.

Footage from state broadcaster CCTV showed windows of nearby houses blown out from the force of the explosion. An aerial view of the blast area showed a large swath of destruction in an industrial park, where multiple fires still raged.

A CCTV reporter on the scene said that toxic fumes were coming from the blast site.

At least six people were killed and 30 seriously injured, while numerous others in the vicinity were slightly injured, city officials said on Weibo late on Thursday.

"At present, on-site rescue is still going on ... The cause of the accident is under investigation," officials said.

Injured residents near the site of the explosion have been sent to hospital for treatment, according to local authorities.

Medical staff, as well as personnel from the public security bureau and fire department, have been sent to the scene, they added.

Buildings knocked down

According to official news agency Xinhua, citing local authorities, the explosion occurred following a fire in a fertiliser factory in a chemical industrial park.

Workers near the site of the blast were trapped after shockwaves from the explosion knocked down nearby factory buildings, the report said.

Workers covered in blood were seen running out of the factory, Xinhua added, citing witnesses.

Images broadcast by state media showed an enormous explosion, with flames engulfing the top of the chemical plant.

Other shots showed thick grey smoke billowing skyward from the site of the blast.

History of industrial disasters

Industrial accidents are common in China, where safety regulations are often poorly enforced.

In November, a gas leak caused an explosion at a PVC production plant in a northern Chinese city that will host the 2022 Winter Olympics, killing 24 people and injuring 21 others.

A report published by local authorities in February revealed that the Chinese chemical firm responsible for the accident had concealed information and misled investigators.

Last July, a blast at a chemical plant in southwest Sichuan province left 19 dead and 12 injured.

The company had undertaken illegal construction that had not passed safety checks, according to local authorities.

And 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 $1billion in damage and sparked widespread anger at a perceived lack of transparency over the accident's causes and its environmental impact.