SHANGHAI (NYTIMES) - Since the coronavirus pandemic erupted in China, the country has grown adept at swiftly smothering virus flare-ups by ordering residents across entire cities to line up for nucleic acid tests that can pinpoint carriers. So officials snapped into action after a cluster of infections linked to Pudong International Airport in Shanghai grew over the weekend.

On Sunday (Nov 22), Pudong International Airport ordered cargo handlers and other potentially exposed workers to immediately undergo tests. But this time, the plan faltered badly.

The urgent order prompted a crush of hundreds of workers who converged on an airport parking garage that had been converted into a temporary test centre, and a video that spread first on Chinese social media showed guards in protective suits struggling to hold back a seething, anxious crowd trying to walk up a ramp.

Another video shared by Shanghai residents appeared to show a worker who had fainted being carried out of the garage.

Shanghai authorities ordered the blitz of tests after testing confirmed five cases linked to the airport since last Friday, including three workers and two of their spouses.

The scenes of workers jammed together drew criticisms that the poorly organised testing only exposed them to greater risks of infecting one another, and the video images quickly began to disappear from Weibo and WeChat, China's two main social media platforms, as censors apparently stepped in.

"Even if the outbreak is urgent, there aren't even the most basic safety and distancing measures," said one comment widely shared on Weibo. "This can cause big problems."

The government moved quickly to combat the anxiety about the cluster and scenes of mayhem. Shanghai police issued pictures of airport workers in orderly lines, waiting to be tested in the garage - apparently after officials had restored control.

"Currently everything is normal and there is an orderly queue for tests," said The Paper, a news website based in Shanghai.

Chinese health officials appear likely to step up tests and disinfection at airports and other sites that handle imported goods.

Earlier this month, tests revealed two infections among freight handlers at Pudong Airport, and Chinese experts have repeatedly raised the theory that the virus may be carried on goods from abroad.