The Chinese city of Qingdao says it is planning to test its entire population of more than nine million people for the novel coronavirus in five days.
Health authorities said on Monday that about a dozen new infections were detected over the weekend in the eastern coastal city.
Most of the new infections were linked to a hospital.
It added that more than 140,000 people, mainly working in the health sector, were tested immediately after the first positive COVID-19 cases emerged.
Recently China has only recorded coronavirus infections imported from abroad.
The country brought the virus’ spread under control with tough measures such as locking down cities where millions live, strict isolation and entry bans.
There have been several limited localised COVID-19 outbreaks, as in Qingdao now, but they have been swiftly halted. Mass testing was also used in those cases.