The city of Shenzhen in south China's Guangdong Province on Tuesday registered three new asymptomatic cases of the novel coronavirus, local authorities said.
The three tested positive for the virus and were reported as asymptomatic cases on Monday.
Since May 21, seven people have been identified as asymptomatic cases in Yantian District's port area, the municipal government's information office said at a press conference on Tuesday evening.
Their infection is mainly linked with workers boarding international freight ships to load and unload cargo. Most of the cases occurred aboard the same global freight ship on May 17, the information office said.
The gene sequencing analysis on the five earliest cases of the city's recent outbreak indicates that the viral sequences of the five persons are highly homologous to that of the mutant strain first found in Britain, said the city's center for disease control and prevention.
The Yantian District is home to Yantian port, a major foreign-trade port in China.