The company that makes Apple's iPhones suspended production at a factory in China on Monday after a riot involving as many as 2,000 employees at a dormitory left 40 people injured.
The fight, the cause of which was under investigation, erupted on Sunday night at a privately managed dormitory near a Foxconn Technology Group factory in the northern city of Taiyuan, the company and Chinese police said.
The company and police said the violence was not work-related and grew out of a personal dispute, but comments posted on Chinese Internet bulletin boards said it might have erupted after a security guard hit an employee.
A police statement reported by the official Xinhua News Agency said 5,000 officers were dispatched to the scene.
The technology blog Engadget noted that a riot at Foxconn's Chengdu factory that broke out in June was apparently caused by a dispute between workers and a local restaurant order.
An "undercover report" by a Chinese news outlet cited by Engadget claimed that the Taiyuan factory produced the back casing of Apple's new iPhone 5 and suffered from "harsh" management policies.
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 suspend work on Monday and reopen Tuesday.
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 about 1.2 million workers in factories in Taiyuan, the southern city of Shenzhen, in Chengdu in the west and in Zhengzhou in central China.
The fight in Taiyuan started at 11pm on Sunday, "drawing a large crowd of spectators and triggering chaos,'' a police spokesman was quoted by Xinhua as saying.
Order was restored after about four hours and several people were arrested, said the company, a unit of Taiwan's Hon Hai Precision Industry Co. It said 40 people were taken to hospitals for treatment.
Photos posted on microblog service Sina Weibo showed broken windows, a burned vehicle and police with riot helmets, shields and clubs. Phone calls to police headquarters and the Taiyuan city hall were not answered.
People reached by phone at restaurants and other businesses in the area said they had no details about the clash. The company has faced scrutiny over complaints in the past about wages and working hours.
It raised minimum pay and promised in March to limit hours after an auditor hired by Apple found Foxconn employees were regularly required to work more than 60 hours a week.