The fight, the cause of which was under investigation, erupted at a private dormitory near a Foxconn Technology factory in Taiyuan, the company said.
A police statement reported by the official Xinhua News Agency said 5000 officers were dispatched to the scene. The Taiwanese-owned company declined to say whether the factory was involved in iPhone production.
It said the facility, which employs 79,000 people, would reopen today.
Foxconn makes iPhones and iPads for Apple and also assembles products for Microsoft and Hewlett-Packard. It is one of China's biggest employers, with some 1.2 million workers in factories in Taiyuan, Shenzhen, Chengdu and Zhengzhou.
The fight in Taiyuan "drew a large crowd of spectators, triggering chaos", a police spokesman was quoted as saying.
The violence did not appear to be work-related, the company and police said. Comments posted on internet bulletin boards said it might have erupted after a security guard hit an employee.