Wuhan, ground zero for the coronavirus pandemic, reported 11 new asymptomatic cases today, according to the central Chinese city’s Municipal Health Commission.

The cases were discovered in multiple districts across the city, a statement from the commission said.

An ambitious screening program that aims to test all 11 million of the city’s residents is underway in an attempt to curb the spread of the virus from a recent cluster of local cases.

The commission’s statement said that on May 13, 67,026 people were tested in one day in Wuhan.

Some 559 asymptomatic cases were under medical observation, as of May 13.

On Thursday, state-run news agency Xinhua reported that: “Wuhan has detected several to more than a dozen asymptomatic infections every day. Although these asymptomatic infections are all treated in isolation, they still cause concern in the society.”

Wuhan has officially recorded 3,869 deaths from Covid-19 — the majority of China’s fatalities from the disease. The city has confirmed more than 50,000 coronavirus cases in total.