explosion in China
© ReutersSeveral buildings reportedly collapsed in a nearby residential area.
An explosion has rocked the port city of Ningbo in eastern China's Zhejiang province, leaving multiple casualties and causing nearby buildings to collapse, Chinese news agency Xinhua has reported.

The blast, which occurred in a factory at about 8:50 a.m. on Sunday, shattered windows up to a kilometer from the site, the South China Morning Post reports.

China Central Television reporting that at least two people have died and another two are have received critical injuries as a result of the blast.

Footage of the scene broadcast by the People's Daily shows a huge cloud of smoke dwarfing nearby tower blocks. The cause of the explosion is unknown. Multiple casualties were reported by local police, who said paramedics are treating people for serious injuries.

Several buildings collapsed in a nearby residential area that had already been cleared of people, according to Zhejiang Daily. Police told Reuters the area had been marked for demolition.

Rescue work and investigation into the cause were underway, police said in a statement issued on their verified Weibo account.

Pictures circulating on both state and local media showed a street littered with debris and shattered glass and the arrival of several fire engines. Reuters could not independently verify the authenticity of the photographs.

Blasts and other accidents are common in China due to patchy enforcement of safety rules, although the government has pledged to improve checks to stamp out such incidents.