The official Xinhua News Agency said one other person was injured in the fire, which broke out at 3:30 p.m. in Shantou city in Guangdong province and was put out in half an hour.
The Southern Metropolis Daily said in an online report that the victims were all women aged 18-20.
It said the cause of the fire was arson, according to an initial police and fire investigation.
A photo accompanying its report showed a four-story building, lined with windows on each floor, completely blackened. The fire had not spread to an adjacent building.
Senior provincial officials set up a team to investigate the cause of the fire and step up safety measures to avoid similar fatal fires, Xinhua said in its brief report. The factory made underwear, it said.
Last month, a fire at a clothing factory in Bangladesh killed 112 people and highlighted dangerous workplace conditions. Workers who survived the fire said exit doors were locked.