Apple’s main iPhone manufacturing plant in China saw violent protests erupt as workers clashed with security personnel, due to harsh measures implemented to quell a Covid-19 outbreak.

The Foxconn Technology Group plant ground to a halt as workers burst out of dormitories early Wednesday, and began clashing with white-clad security guards, who they vastly outnumbered. Videos filmed by witnesses showed workers pushing past the security, and several security guards beating people with sticks as onlookers shouted “Fight, fight.” At one point workers could be seen rocking a Police car they had surrounded while screaming.

Unpaid wages and fears over the virus outbreak triggered the conflict overnight, according to one witness. On Wednesday Police and security arrived, and the clashes began.

In one video, workers confronted a manager, saying, “I’m really scared about this place, we all could be Covid positive now.” Another worker said, “You are sending us to death.”

Tensions at the plant have been building since October, when the lockdown began. The 200,000 workers who now inhabit what has come to be called “iPhone City” were thrust into isolation, as they scrounged for medications, and were forced to subsist on the most basic food supplies.

Last month, many broke free and fled the plant. In recent weeks, Foxconn and the local government promised unusually high wages and better working conditions, and appeared to have gotten the situation under control. However Wednesday morning’s protest would seem to indicate that is no longer the case.

The situation at Foxconn’s plant highlights the risks many companies which are dependent on Chinese manufacture now face in the modern era of China’s “zero-Covid” policies, and uncertain trade relations.

Zhengzhou is responsible for producing roughly four out of five of Apple’s premier handsets, and the vast majority of the most advanced iPhone 14 Pro units. Last month Apple warned that shipments of the new premium iPhone were smaller than the company had anticipated, just as it heads into the critical holiday shopping season.

For weeks the plant has managed to keep only some production lines operational, by operating in what it calls a “closed loop,” a self-contained bubble which limits worker’s contact with the outside world.

Both Apple and Foxconn have acknowledged the problem, and have said they are working to replace staff which have left, and get the production lines fully operational as soon as possible.