The blast occurred Saturday in an abandoned kiln being used illegally to produce fireworks in the city of Weifang in Shandong province, said the official Xinhua News Agency.

The local government first reported three people had been killed, but the death toll rose to 13 as more bodies were found Sunday, it said.

Accidents in Chinese factories are common, with thousands dying every year in part because of lax enforcement of safety rules. Fireworks factories, many of them illegal, are notoriously unsafe.

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