Hong Kong authorities said Saturday they blocked part of a crowded neighborhood and started testing everyone there. This is one of the most dramatic measures that Chinese territory has taken since the coronavirus appeared there last winter.

The local government said Saturday that it had restricted access to some parts of the Jordan district and that people there would be prevented from leaving the country until tested, the first such lockdown in Hong Kong. Battalions of police officers were seen guarding the perimeter as health workers in head-to-toe protective gear walked in.

About 200 buildings in the Jordan region were affected and more than 1,700 police and other officers were expected to be deployed, the South China Morning Post reported. Jordan – which is a mix of office buildings, apartment towers, and shabby pedestrian streets – is one of Hong Kong’s busiest neighborhoods.

Officials said 162 confirmed coronavirus cases had been registered in 56 buildings in Jordan in the first 20 days of January.

The government plans to complete testing of residents of the restricted area within 48 hours so residents can go to work on Monday morning. In a statement, the measures were described as an attempt to “completely sever local chains of transmission and alleviate the concerns and fears of residents”.

During much of the pandemic, the daily caseload in Hong Kong, a financial hub of 7.5 million people, was relatively small compared to other cities of its size. Even now, fewer than 10,000 coronavirus cases and 168 deaths have been recorded.

But new infections in the past few months have led the government to revert to their toughest social distancing measures and require mandatory testing in some areas, including Jordan. As of Saturday, an average of 55 cases a day had occurred in Hong Kong for the past week.