BEIJING, China (AP) — Beijing will conduct mass testing of most of its 21 million people, authorities announced Monday, as a new COVID-19 outbreak sparked stockpiling of food by residents worried about the possibility of a Shanghai-style lockdown.

The Chinese capital began mass testing people in one of its 16 districts where most of the new cases have been found. The city also imposed lockdowns on individual residential buildings and one section of the city. Late in the day, health officials said the testing would be expanded Tuesday to all but five outlying districts.

While only 70 cases have been found since the outbreak surfaced Friday, authorities have rolled out strict measures under China’s “zero-COVID” approach to try to prevent a further spread of the virus.

The city of Anyang in central China and Dandong on the border with North Korea became the latest to start lockdowns as the omicron variant spreads across the vast country of 1.4 billion people.

Beijing health officials said 29 new cases had been identified in the 24 hours through 4 pm Monday, raising the total to 70 since Friday.

The city has ordered mass testing across sprawling Chaoyang district, where 46 of the cases have been found. The 3.5 million residents of Chaoyang, as well as people who work in the district, need to be tested on Monday, Wednesday and Friday.

Testing sites were set up overnight and in the early morning in Chaoyang at residential complexes and office buildings around the district. Residents and workers lined up at the temporary outdoor stations for a quick throat swab by a worker in full protective gear. The testing is free.