Two people have been killed and more than 30 people are injured in an explosion south of Shanghai, Chinese state television reports.

The cause of Sunday’s blast at a factory premises in the harbour city of Ningbo was not immediately clear.

Initial reports spoke of an explosion in a building in the district of Jiangbei which was due to be razed to the ground.

Several buildings in the area collapsed and window panes were shattered within a one kilometre radius as a result of the blast, the South China Morning Post reported.

Bystanders said the explosion might have been caused by a gas pipeline that was damaged during demolition work, but the Ningbo gas company said it had no lines in the area, the newspaper China Youth Daily reported.

Two people were found dead and more than 30 people were injured after a major explosion hit China’s eastern port city of Ningbo on Sunday. Photo: Getty

Photos on News.163.com showed an injured woman being carried away on a man’s back and what appeared to be the body of man lying in the debris of a wrecked building.

Video clips on multiple websites showed a white cloud of smoke rising above the explosion site and rolling across nearby buildings.

A photo on news.ifeng.com showed a room in an industrial building with a floor-to-ceiling hole blown through an exterior wall. Other photos showed apartments with windows blown out and glass littering the floors.

-with agencies