Foxconn confirmed that a “personal dispute” escalated into an incident involving about 2,000 workers, injuring 40 of them.
Police later dealt with the situation near the facility in Taiyuan, which employs about 79,000 workers.
Foxconn has previously been accused of having poor conditions for its workers.
Investigation launched
Foxconn said the incident started on Sunday at about 2300 local time (1500 GMT) in a dormitory near the Taiyuan manufacturing facility in Shanxi province.
Internet users in China posted pictures on microblog sites which they said had been taken at the scene showing windows of nearby shops smashed and police vehicles overturned.
Some photos showed police and paramilitary officers in riot gear being deployed to the scene.
The dispute was brought under control by police at about 0300.
About 40 people were taken to hospital and a number of individuals have been arrested, the company said.
The cause of the brawl is unknown, but Foxconn said local authorities were now conducting an investigation into the incident.
The company also said that the dispute did not appear to have been work-related.
The plant makes electronic components for cars and consumer devices.
Earlier in the year a fight broke out in a restaurant at a Foxconn plant involving about 100 workers.
State media reported that the incident in Chengdu “was triggered by a conflict” between a group of workers and a restaurant owner.
A string of suicides at Foxconn last year put the spotlight on working conditions at its factories.
Foxconn has since agreed to reduce hours, protect pay and improve staff representation.