Foxconn Technology Group and police said the cause of the unrest Sunday night was under investigation, but it comes amid a series of violent protests by workers in areas throughout China over grievances about pay and working conditions. Foxconn and police said as many as 2,000 employees were involved and 40 people were reported injured.
Foxconn manufactures Apple Inc.'s new iPhone 5, which debuted last week in the United States and eight other countries, but declined to say whether the one-day suspension would affect supplies of that model. Apple has a three- to four-week backlog of online orders as it ramps up production to meet demand.
News reports and witnesses said the violence that erupted Sunday night in Taiyuan in northern China stemmed from a confrontation between a factory worker and a guard that quickly escalated. One employee reached by telephone said the violence was fueled by anger among factory workers over treatment by Foxconn security guards and managers.
"Foxconn, some supervisors, and security guards never respect us," said the employee, who asked not to be identified by name. "We all have this anger toward them and they (the workers) wanted to destroy things to release this anger."
Production at the Taiyuan factory resumed on Tuesday, according to an employee who answered the phone at the factory's labor office. He would give only his surname, Li.
Labor tensions in China have been aggravated by a slowing economy that is squeezing employers and a communist system that prohibits independent labor unions.
Many factories and other businesses have unions but they must be part of the government-sanctioned All-China Federation of Trade Unions. Workers complain leaders of local branches often are allied with management and fail to stand up for the workforce.
That means grievances over pay, working hours and other conditions spiral into strikes and public protests. In some cases, ACFTU representatives have scuffled with striking employees outside factories.
"They have no other way of voicing their grievances," said Geoffrey Crothall, communications director for China Labour Bulletin, a Hong Kong organization that promotes employee rights in China. "There are no formal channels of communication or ways of resolving grievances through peaceful negotiation."
Foxconn, owned by Taiwan's Hon Hai Precision Industry Co., has faced scrutiny over workers' complaints about wages and working hours. The company 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.
Foxconn makes iPhones and iPads for Apple Inc. and also assembles products for Microsoft Corp. and Hewlett-Packard Co.
It is one of China's biggest employers, with some 1.2 million workers in factories in Taiyuan, the southern city of Shenzhen, in Chengdu in the west and in Zhengzhou in central China.
Foxconn employees have complained about what some call "military-style" management.
"Workers are expected to obey their manager at all times, not to question but simply to what they are told," Crothall said. "That atmosphere is not conducive to a happy or contented workforce. It's a very dehumanizing way of treating workers."