SHANGHAI, (Reuters) – Quanta Shanghai Manufacturing City is a good location to introduce China’s “closed loop” management system. It prevents the spread COVID by requiring staff to stay and work in a protected bubble.

Spread over 20 football field-sized lots, the campus contains factories, housing quarters for around 40,000 workers and even a supermarket.

However, Quanta was unable to defend itself against COVID-19 and the system crashed into chaos on Thursday.

Video footage posted online shows more than 100 Quanta workers physical assaulting security guards and jumping over factory gates. They were apparently trying to escape the factory, amid reports that COVID was being tested on workers.

Quanta’s turmoil highlights the difficulties Shanghai has to overcome to bring its factories back to life. This is despite the fact that China’s COVID policy of “dynamic zero” still holds much of Shanghai, a city with 25 million people, behind bars.

Quanta, a Taiwanese company that manufactures circuit boards for Tesla (NASDAQ) and about three quarters of Apple’s worldwide MacBook production (NASDAQ:), is responsible for approximately three quarters of Apple’s total global MacBook production.

Quanta didn’t respond to my request for comment about the videos. They were posted on Chinese social media platforms and then removed. Apple declined to comment while Tesla refused to respond to requests for comment.

Quanta established its closed loop to restart factory work on April 18. It employed approximately 5%, or 2000 employees. Plans to double that number by April 22. China’s state media praised the start as an example of Shanghai keeping the doors open and adhering strictly to COVID standards.

DAILY CASES

However, daily cases at an address connected to the campus have been reported from March 26 through May 4, according Shanghai government data. Quanta does not reveal the total number of cases among its staff.

Weibo, NASDAQ:), began to show calls asking for help in bringing attention to positive Quanta cases starting on April 6, five days following Shanghai’s citywide lockdown.

As the month progressed, more people started posting pictures and accounts to Douyin. This is the Chinese equivalent to TikTok. It showed many workers waiting for buses to take them to the central quarantine facility.

The group also recorded videos of them resting at Shanghai’s National Exhibition and Convention Center. This is one of Shanghai’s most important quarantine centers.

Reuters couldn’t independently verify footage. Two employees and a person familiar with campus operations reported multiple infections.

“Each dormitory reported positive cases every day, and finally everyone became positive,” stated one of two workers. He gave his name as Li and added that there were eight cases within his room.

The employees claimed that the cases weren’t isolated often for many days after they were tested positive. Someone with direct knowledge of campus operations also stated that the isolation areas were inadequate, which led to the spread of infections.

Employees claimed that Thursday’s chaos was caused by the spread of rumors about positive cases among workers in factories.

They were terrified by an instruction telling them not go back to their dormitories. This raised fears about being locked up in the plant.

The videos were removed by the weekend. However, there was still discussion on Weibo, Douyin and other platforms, one user simply saying “What a mess”.