Foxconn has resumed production at its Taiyuan plant in Northern China, which was halted on Monday following a riot.
The company said that the one-day stoppage would not affect its output.
Foxconn is the world's largest contract manufacturer of electronics, making brands such as Apple, Microsoft, Nokia and Dell.
Workers at the plant said that the unrest had been sparked when a worker was severely beaten by security guards on Sunday evening.
The company is investigating the incident, but said it did not think it had been work-related.
But workers interviewed by Reuters said that tensions had been rising because workers had been moved from other Foxconn plants to Taiyuan to help with production of Apple's new iPhone 5.
Louis Woo, a Foxconn spokesman, said security guards involved in the unrest had been under contract with a third party at a privately-managed factory dormitory. He said that their attitude "is not too good".