The Taiwanese company that makes Apple products has had to close its factory in the northern Chinese city of Taiyuan after a riot involving 2,000 workers.
Foxconn Technology's plant makes automobile electronic components, consumer electronic components and precision mouldings.
One employer told the Reuters news agency the factory makes Apple's new iPhone 5.
Foxconn says about 40 people were taken to hospital for medical attention and a number were arrested.
China's Xinhua News Agency reports that about 5,000 police were sent to bring the riot under control.
The factory employs about 79,000 people at Taiyuan.