AP Photo

Shortly before midnight on Sunday, a fight among assembly-line workers at the Apple supplier, Foxconn, escalated into a riot, involving some two thousand members of the staff, and perhaps the guards, that reportedly left forty people injured.

The state-news service said that five thousand police moved in to restore control. The plant, which has seventy-nine thousand workers in the coal-country city of Taiyuan, shut down. Reporters at the gates saw broken windows and paramilitary police with riot shields, helmets, and batons guarding the entrance, while a loudspeaker urged calm. After twenty-four hours, Foxconn reopened the plant Tuesday.

Though most of the iPhone assembly is done elsewhere, workers said that the iPhone was being made there, too, so the story leapt...