CHANGSHA - Thirteen people have been confirmed dead and one more remained missing after an explosion at a firework plant in central China's Hunan Province on Monday, local authorities said on Tuesday.

The blast happened at around 3 p.m. Monday at the Nanyang Export Fireworks Factory in Baofeng Village of Liling City when 47 workers were at the scene, the rescue headquarters said.

The blast also injured 33 people, including three passersby. Three workers were unhurt.

Four severely injured have been transferred to a better hospital in Zhuzhou City. Twenty-six remained hospitalized in a hospital in Liling and three slightly injured have returned home.

Small explosions were again heard at the scene in the early morning.

The factory was leveled to ground and the surrounding areas were scattered with debris. Several cars inside the plant were burned down, several nearby houses collapsed and windows of more village houses were shattered.

A search operation is still under way with three excavators continuing clearing the debris.

Liling City is a major production base for China's fireworks, which play a major role in traditional festival celebrations like the Lunar New Year.

The city government said the factory was licensed and the cause of the explosion is under investigation.