The fire broke out on Sunday at a factory in Ninghai county, said the local government on its official Weibo account.
The incident, which is under investigation, occurred at a facility owned by the Ruiqi Daily Necessities Company.
Among eight people rescued from the fire, three were injured and sent to hospital for medical treatment, said Ninghai authorities.
It made for a deadly weekend on the mainland ahead of the 70th-anniversary celebrations on Tuesday.
A packed bus collided with a truck in Jiangsu province on Saturday, killing 36 people. (AFP)