The economic zone at Zhengzhou Airport in central China entered seven days of “static management” on Wednesday, local authorities said. About 600,000 people live in the district.

Static management is the term used for lockdowns as an infection control measure in China. This means that no one can enter or leave the industrial area for the next week, except those who deliver food or medicine. Everyone who lives and works in industrial estates now has to be tested every day.

The iPhone factory is run by Taiwanese company Foxconn and has several hundred thousand employees.

Last week, images emerged on social media showing thousands of workers fleeing the factory site on foot. Since mid-October, several thousand employees have left the factory following allegations that coronavirus patients were not receiving treatment.

Foxconn has not provided details of the situation, but said it is testing employees daily and practicing strategies that involve employees staying in the workplace without contact with the outside world.

Authorities did not say whether the isolation was linked to coronavirus infections at the factory. In a separate announcement, it said that 64 cases of infection had been detected in Zhengzhou in the past 24 hours. A further 294 asymptomatic cases have been detected in the city of 12.4 million, he added.