The workers were dismantling the aluminium plant in the provincial capital of Zhengzhou City when a piece of falling equipment hit the employees of the engineering and construction company, said the officials of the Henan branch of the Aluminium Corporation of China, which owns the plant.
Eight other workers who were injured in the accident have been admitted to hospital, state-run Xinhua news agency reported.
According to police, 23 people were working at the site when the accident occurred.