BEIJING — Health officials in China say six more people have become ill with COVID-19 in a southwestern Chinese city on the border with Myanmar. That brings the confirmed total in the Yunnan province city of Ruili over the past two days to 12, including three Myanmar citizens.

The Yunnan Health Commission said Thursday that 23 other people have tested positive for the coronavirus without showing symptoms of illness. Of those, 13 were Chinese and 10 were Myanmar nationals.

Officials say more than 20,000 tests have been administered so far. City authorities plan to test Ruili’s entire population of about 210,000 people, and require them to quarantine at home for one week.

The residential compound where the infections were found has already been locked down.

China has largely eradicated local transmission of coronavirus and takes strict measures whenever a new cluster emerges.