Beijing | At least 21 people were killed and 61 others injured in a massive explosion at a fireworks factory in China's Hunan province, officials said on Tuesday.

The explosion occurred on Monday afternoon at the plant operated by the Huasheng fireworks manufacturing and display company in Liuyang, a county-level city under Changsha, the provincial capital.

Videos circulating on Chinese social media showed massive destruction of property spanning several kilometres.

More than 480 rescuers, organised into five teams, have been deployed for relief operations, with three rescue robots pressed into service.

Rescue officials said 21 people were killed and 61 others were injured. The injured have been rushed to hospitals for treatment, while a second round of search operations is underway.

China is a leading manufacturer and exporter of fireworks.

As the explosion site is located near two black powder warehouses, the rescuers have evacuated nearby residents and set up a buffer zone to prevent a secondary accident, the state-run Xinhua news agency reported.

The Ministry of Emergency Management has dispatched experts to the scene to guide rescue efforts.

The person in charge of the company has been detained by police and the cause of the accident is being investigated, the report said