North China's Tianjin Municipality has entered "wartime" mode after a new local COVID-19 infection was reported, local authorities announced Sunday.

The latest development comes after a worker at a cold storage facility in the port city tested positive for COVID-19 and is at a designated hospital for treatment.

The 38-year-old man had no contact history with other confirmed or suspected cases but was exposed to imported frozen food during his work. Doctors diagnosed him as a mild case. 

Tracing his close contacts, collecting and testing environmental samples and disinfection work are underway.

On Friday, the Tianjin Municipality received a notification from Dezhou City in eastern Shandong Province that samples of frozen food packaging imported through the port tested positive for the novel coronavirus.  

Tianjin immediately started nucleic acid screening of the related frozen food, cold storage area, transport vehicles and all the close contacts.  

To date, only a worker and a door handle at a cold storage area have tested positive. The test results of all the other environment samples remain negative.  

The cold storage involved has been sealed, and the provinces and cities that received food from that area have been notified about the situation.  

Since July, virus contamination in frozen food imported from countries with ongoing epidemics has been reported in nine provinces in China.  

Last month, Chinese researchers warned of a high possibility that cold chain logistics could become a new transmission route for the novel coronavirus. They also concluded that imported food via cold chain from high-risk regions overseas might have been the origin of the unexpected COVID-19 resurgence in Beijing in June. 

Read more: Origin of COVID-19 resurgence in Beijing: Cold chain food contamination 

(Cover: Health workers conduct a nucleic acid test on a resident in Tianjin, September 19, 2020. /VCG.)