Three of the injured were in critical condition, the official Xinhua News Agency said.
The Southern Metropolis Daily said witnesses heard three blasts at the Fuhua Engineering and Manufacturing Co. factory in Foshan city. The blasts destroyed the facility’s walls and ceiling and also damaged a nearby glass factory and other plants.
Pictures on the newspaper’s website showed panels blown off the building’s structure and people lying injured on the ground. Xinhua said the factory was closed for cleaning at the time of the blast.
Officials were investigating the cause of the explosion, it said.