Foxconn denies that workers staged a strike on Friday to protest working conditions on the I-phone five's production lines.
It admits there were isolated "disputes", but says they were addressed and work did not stop.
But both a worker's advocacy group and Chinese state media say there was a work stoppage that temporarily paralyzed production lines.
Workers are said to be outraged by what they describe as management's "overly strict demands."
Apple did not respond to messages from CNN seeking comment.