Media playback is unsupported on your device Media caption Six killed in Yancheng chemical plant explosion

Six people have been killed in a blast at a chemical plant in Yancheng, eastern China, local authorities say.

Thirty people were also injured in the explosion, which took place at about 14:50 local time (06:50 GMT) at the plant run by Tianjiayi Chemical.

The blast was caused by a fire at the factory, which makes fertiliser, officials told local press.

China's earthquake administration reported a tremor equivalent to 2.2-magnitude at the time of the explosion.

Image copyright Getty Images Image caption Dozens were injured in the explosion, which was reportedly started by a fire at the plant

Images on social media showed a fireball exploding at the site, billowing clouds enveloping the area, injured people and damage to buildings.

Officials quoted by Reuters said: "At present, on-site rescue is still going on... The cause of the accident is under investigation."

Image copyright Getty Images Image caption The cause of the accident is under investigation

State news agency Xinhua said shockwaves from the blast had brought down nearby factory buildings, trapping workers.

Tianjiayi Chemical, founded in 2007, has received six government penalties in the past over waste management and air pollution, according to the South China Morning Post.

Several chemical plants operate in the nearby area, according to local press.

Industrial accidents are common in China due to poorly enforced safety regulations, and authorities have pledged to improve standards.

More than 160 people died in 2015 after two massive explosions in the port of Tianjin in northern China.