Hours after the fire broke out at the Huiteng Shoes factory around noon (0400 GMT), authorities feared people were still trapped inside the building in Jinjiang City, Fujian Province.
President Xi Jinping said the fire resulted in "heavy human losses", with state news agency Xinhua later citing a preliminary toll of 28 dead.
Footage shared by state television CCTV showed firefighters dousing the facade and interior of a large, multi-storey white building with fire hoses, as thick black smoke billowed out of broken windows.
People could be seen taking refuge near the windows and on the roof of the building, while the blaze raged in the lower floors.
CCTV said 500 firefighters and other emergency personnel were on the scene.
