At least 20 people were killed and more than 30 injured in a large fireworks blast in China's southeastern Fujian province, state television reported yesterday.

The explosion occurred at 10:50pm local time Tuesday inside an old wooden shed used to illegally manufacture and store large quantities of fireworks, China Central Television said.

The force of the blast destroyed homes 60 metres away and torched four nearby residential buildings.

Rescue workers yesterday were still searching for possible casualties and authorities said an investigation was underway.

Officials said they had checked up on factories in the area producing illegal fireworks after five people were killed in a blast last month, but many of these makeshift facilities were able to easily transfer locations.

China is the world's biggest producer of fireworks, with people in rural areas often illegally making them in their homes under unsafe conditions.

Chinese authorities have repeatedly vowed to crack down on illegal and hazardous fireworks factories, but accidents continue to happen.

Most recently, 35 people died and 103 were injured in a fireworks factory explosion last month.