The Cabinet Office says it made a referral to police based on information discovered while preparing submissions for a public inquiry into the pandemic.

Residents are required to stay in their homes through the end of Sunday and must submit to temperature checks multiple times each day, according to NK News, which monitors North Korea.

China's axing of its stringent controls last month has unleashed Covid on a 1.4 billion population that has little natural immunity having been shielded from the virus since it emerged in its Wuhan city three years ago.

As many residents welcome a relaxation of measures that have crippled businesses and stoked unemployment, some scooped up by China's security apparatus face an anxious wait about their fate.

The country logged over 5,600 new Covid cases Monday – almost half in Guangdong province, a manufacturing hub in the country's south home to major ports.

The move comes after images emerged on Chinese social media showing people breaking out of the facility, which is run by Taiwanese tech giant Foxconn and employs hundreds of thousands of workers.

US Education Secretary Miguel Cardona describes the test results as 'appalling' but says they are a call for action.

The city of 21 million people on Thursday reported 18 new locally transmitted cases for the previous day, bringing the tally for the past 10 days to 197.

Building lockdowns are springing up across Shanghai and Chengdu, the capital of southwestern China's Sichuan province, was locked down in September.

The mega city Chengdu, which has most recently battled with heatwaves, power cuts and an earthquake, was locked down on Sept 1 after detecting a number of cases.

China is sticking to its stringent zero-Covid policy, even as most other countries have relaxed restrictions and chosen to live with virus.

Chengdu, which reported 157 domestically transmitted infections, is the largest Chinese city to be locked down since Shanghai in April and May.