SHENZHEN -- The southern Chinese metropolis of Shenzhen reported one new asymptomatic case of COVID-19, local health authorities announced Wednesday.

The case was a close contact of an imported COVID-19 case confirmed Tuesday, the municipal health commission said.

The imported case was a Hong Kong truck driver who transports goods between Shenzhen, South China's Guangdong province, and Hong Kong. Authorities have placed 52 people under isolated observation, including the driver's 11 close contacts.

The asymptomatic case, surnamed Yang, went home in the truck of the Hong Kong driver on Sunday and Monday. Yang, 54, was put under isolated observation Tuesday after the truck driver was tested positive for the novel coronavirus Monday.

Yang tested negative for the virus on Tuesday, but tested positive on Wednesday. Yang was diagnosed as an asymptomatic case and was in stable condition.

Local authorities will conduct nucleic acid tests on residents living in the same residential community as the new asymptomatic case.