China’s Qingdao city says it will test its entire population of more than nine million for COVID-19 over five days with new cases apparently linked to a hospital treating imported infections.

The city reported six new COVID-19 cases and six asymptomatic cases as of late October 11.

Most were linked to Qingdao Chest Hospital.

The National Health Commission’s tally of 21 confirmed COVID-19 cases in mainland China for October 11 was published after Qingdao’s announcement but did not include any confirmed infections in the city and it was not immediately clear why.

The number of new asymptomatic cases, which China does not count as confirmed cases, rose to 32 from 23 a day earlier, the NHC said.

It did not offer a breakdown on where the new asymptomatic cases were reported, though it said 29 were imported infections.

Daily COVID-19 infections in mainland China have fallen drastically from peaks early in 2020 but the country remains on high alert to prevent painful lockdowns that led to an outright contraction of the world’s No. 2 economy.

Qingdao has already locked down Qingdao Chest Hospital as well as the emergency department of its central hospital.

Buildings the infected individuals live in have also been locked down as part of containment measures.

The total number of confirmed COVID-19 cases in mainland China stands at 85,578, with the death toll unchanged at 4634.