Millions of people in Wuhan will be tested for the novel coronavirus within the coming days, after a new cluster of cases emerged despite a strict 76-day lockdown that was intended to eliminate the virus from the central Chinese city.

Over the weekend, six new cases were reported in the city, the first in 35 consecutive days. None of the new cases were imported from overseas, sparking concern that the infection could still be spreading in the city where the virus is thought to have first emerged.

In response to the outbreak, authorities in Wuhan will conduct city-wide nucleic acid testing over a period of 10 days, according to an emergency notice issued by local authorities and circulated by state run media outlet The Paper.

Nucleic acid tests work by detecting the virus’ genetic code, and can be more effective at detecting the infection, particularly in the early stages, than tests which examine a body’s immune response, though the latter are easier to conduct.

The ambitious screening drive, described in the report as a “ten-day battle,” could see up to 11 million people tested — more than the entire population of Greece.

Wuhan was the first city in the world to enter into lockdown and great effort has been expended in an attempt to eliminate the virus.

The city has been gradually returning to normal after that 76-day enforced lockdown lifted on April 8, with residents finally permitted to go outside, though many businesses remain closed.

Despite the ongoing economic pain and trauma, however, Wuhan had been held up as a poster child of China’s effective response to the pandemic, emerging “like a phoenix,” in the words of one state-backed newspaper.

The reemergence of the virus has already had ramifications for the local government. State media reported Monday that Zhang Yuxin, chief official of Changqing, the area where the new cases had been detected, was removed from his post “for failures in epidemic prevention and control work.”

While no new cases of the virus were reported in Wuhan as of Tuesday, any major increase in numbers as a result of the new testing will raise serious questions over the accuracy and transparency of the city’s previous figures. Officials are already facing accusations of covering up the severity of the virus in the earliest stages of the pandemic, and confusion over China’s national figures has been created by several shifts in diagnostic and reporting procedures.

Nor is Wuhan the only part of the country where new cases have been detected. The city of Shulan, in Jilin province in the country’s far northeast, was put under “wartime control mode” Sunday, after 11 people were confirmed to be infected with the virus.

Elsewhere in Asia, South Korea, previously thought to be largely on top of the virus, has also faced a setback this week, with a cluster of new cases detected in Seoul. The country’s president, Moon Jae-in, said Sunday that the fight against coronavirus is “not over until it’s over.”