Thousands of Hong Kong residents were locked down on Saturday in an effort to contain a worsening outbreak of coronavirus in the city.
There have been more than 4,300 cases of coronavirus in Hong Kong since November, making up nearly 40% of the city's total.
Cases in a working-class neighbourhood, the Yau Tsim Mong district, made up half of infections last week.
Sewage testing in the area picked up more concentrated traces of the virus, prompting concerns that poorly built plumbing systems and a lack of ventilation in subdivided units may present a possible path for the virus to spread.
During the 2003 outbreak of SARS in Hong Kong, the virus likely spread through "inadequate plumbing", according to a World Health Organization (WHO) technical analysis that year.
Experts at WHO wrote in 2003 that "inadequate plumbing and sewage systems could continue to enhance the potential spread of SARS and certain other diseases."
Authorities said on Saturday that an area of the Yau Tsim Mong district with 16 buildings will be locked down until residents are all tested.
Residents will not be allowed to leave their homes until they receive test results.
“Persons subject to compulsory testing are required to stay in their premises until all such persons identified in the area have undergone testing and the test results are mostly ascertained,” the government said in a statement.
Hong Kong has previously avoided lockdowns in the city during the pandemic, with leader Carrie Lam stating in July last year that authorities would avoid taking such “extreme measures”.
The restrictions, which were announced at 4:00 am local time in Hong Kong, are expected to end within 48 hours, the government said.
It appealed to employers to exercise discretion and avoid docking the salary of employees who have been affected by the restrictions and may not be able to go to work.
Hong Kong has seen a total of 9,929 infections in the city, with 168 deaths recorded as of Friday.