Hong Kong’s government locked down an area of Kowloon peninsula on Saturday, saying its 10,000 residents must stay home until all of them have been tested for the new coronavirus and results largely determined.

The government said there are 70 buildings in the “restricted area” of Jordan and that it aims to finish the process within about 48 hours, so that people can start getting to work on Monday.

Hong Kong authorities have taken aggressive measures to combat the COVID-19 pandemic in the Asian financial and airline hub, but Saturday’s move is the first lockdown in the Chinese-ruled city.

Many buildings are old and poorly maintained in the small, densely populated area, where subdivided units are common, said health secretary Sophia Chan.

“The infection risk in the community is quite high,” she told a news conference. “After assessment, we think it’s necessary to make a restriction-testing declaration in the restricted area to achieve the goal of zero cases.”

The restricted area has confirmed 162 confirmed cases of COVID-19 this month, and the ratio of virus detected in sewage samples from buildings there was higher than that of other areas.