Authorities in the northern city of Taiyuan sent 5,000 police to restore order after what the plant's Taiwanese owners Foxconn Technology Group said was a personal dispute in a dormitory that erupted into a mass brawl. 

However, some employees and people posting messages online accused factory guards of provoking the trouble by beating up workers at the factory, which employs about 79,000 people and is owned by the world's largest contract maker of electronic goods.

  "The plant is closed today for investigation," Foxconn spokesman Louis Woo told Reuters. It was not clear how long the plant would be shut while police and company officials investigate the violence, but an employee contacted by telephone said the closure could last two or three days. 

Foxconn cited police as saying that 40 people were taken to hospital and a number were arrested, while the state-run Xinhua news agency reported three people were in serious condition.