MOSCOW (AP) — Moscow authorities on Friday began free coronavirus testing for all residents. Under the program announced by Mayor Sergei Sobyanin, tests for coronavirus antibodies, a marker of infection, will be conducted at 30 clinics throughout the city.

The program will allow officials “to know precisely how many Muscovites had coronavirus and developed immunity, how many people are infected or are suspected to have coronavirus,” the mayor said in a blog post Thursday.

Sobyanin said that 70,000 city residents will receive invitations for testing “every few days” and that the city will have the capacity to do 200,000 tests a day by the end of the month. The data obtained during testing will help the city authorities coordinate the work of health care facilities and make decisions on whether to extend or ease lockdown restrictions, the mayor added.

Moscow, with a population of more than 12 million, accounts for half of the country’s more than 262,000 reported infections.

Scientists remain divided over the utility of antibody tests because they essentially can’t detect ongoing infections and it’s still unclear whether the presence of antibodies ensures people will be immune to future infections. There is also varying reliability among the many tests so far developed. The World Health Organization says it is still evaluating the numerous tests available and warns that inaccurate tests could compromise response efforts.