Foxconn, which makes Apple's iPhones, suspended production at a factory in China on Monday after a brawl by as many as 2,000 employees at a dormitory injured 40 people.
The fight erupted 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. A police statement reported by the official Xinhua News Agency said 5,000 officers were dispatched to the scene.
The Taiyuan plant, which employs about 79,000 workers, makes automobile electronic components, consumer electronic components and precision moldings. An employee told Reuters the plant also makes parts and assembles Apple's iPhone 5.
In a statement, Foxconn cited police as saying about 40 people were taken to hospital for medical attention and a number were arrested.
The company said the incident escalated from what it called a personal dispute between several employees at around 11 p.m. local time (11 a.m. ET) on Sunday. It was brought under control by local police at around 3 a.m.
"The cause of this dispute is under investigation by local authorities and we are working closely with them in this process, but it appears not to have been work-related," Foxconn said.
The fight drew "a large crowd of spectators ... triggering chaos," a police spokesman was quoted by Xinhua as saying.
Photos posted on microblog service Sina Weibo showed broken windows, a burned vehicle and police with riot helmets, shields and clubs.
"The plant is closed today for investigation," Foxconn spokesman Louis Woo said.
Foxconn, the trading name of Hon Hai Precision Industry Co and the world's largest contract maker of electronic goods, has seen a few violent disputes at its sprawling plants in China, where it employs a total of about 1 million workers.Video: iProblem? (on this page)
Foxconn also assembles products for Microsoft Corp. and Hewlett-Packard Co. It is one of China's biggest employers.
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 regularly were required to work more than 60 hours a week.
But in June, about 100 workers went on a rampage at a Chengdu plant in southwestern China.
A staff member at the Taiyuan plant said he was told the plant could be closed up to two to three days as police investigated.
"There are a lot of police at the site now," the staff member, who asked not to be named because he is not authorized to speak to media, told Reuters by telephone.
Calls to the Taiyuan police were not immediately answered, while an official at the plant declined to comment when reached by telephone.
Reuters and The Associated Press contributed to this report.