Almost 2,000 workers at a Chinese electronics factory were involved in a mass brawl which has injured 40 people and resulted in the closure of the plant.
Taiwan's Foxconn Technology Group, which has been involved in several controversies involving its working conditions, said that a "personal dispute" began the fight at the Taiyuan factory in the north of China.
The dispute between several of the 79,000 employees at the factory spilled over into a large fight on Sunday evening, in which 40 people were injured after about four hours.
A Chinese news agency said that 5,000 police were sent to contain the fight.
A number of people were also arrested at the factory, Foxconn said.
The factory - one of many that Foxconn operates in China, building electronics for most major firms - is focused on automotive parts and electrical components. It is also used to assemble the iPhone 5, according to workers quoted by Reuters, though that has not been confirmed.
"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.
According to Reuters, workers said police were still at the site and the plant was closed for the day.
Foxconn is the trading name of Hon Hai Precision Industry Co, which employs about a million workers in total across China.
Recently Samsung said it would investigate the Foxconn factories it uses after claims of child labour being used there by China Labour Watch.
Earlier this year about 1,000 workers were reported to have 'rioted' at a Foxconn factory in Chengdu, while Apple appointed labour monitors to respond to further claims of abuse.