Shenzhen, Guangdong province, has tightened COVID-19 prevention and control measures to prevent imported cases from spreading in the city by strictly implementing closed-loop management of truck drivers at cross-border transfer stations.

The city initially implemented closed-loop management of cross-border truck drivers entering from Hong Kong.

Since Sunday, the city, which borders Hong Kong, has required all drivers from Hong Kong and the Chinese mainland to work and stay in designated closed-loop management venues when they enter the city's cross-border transfer stations, Shenzhen's office of port entry and exit said in a statement posted on its WeChat social media account on Monday.

Shenzhen has registered 13,655 cross-border truck drivers who are exempt from quarantine requirements when entering the city as long as they can show negative nucleic acid test results and green health codes.

The city has 17 cross-border transfer stations for trucks that operate between the mainland and Hong Kong every day.

The new measures were introduced after a truck driver in Shenzhen tested positive for the novel coronavirus at a cross-border truck transfer station on Saturday.

Shenzhen authorities said the 35-year-old man had been delivering goods to the Man Kam To Control Point leading to Hong Kong's New Territories. The checkpoint is a major gateway for the transport of fresh food－including vegetables, meat and fish－from the mainland to Hong Kong.

Another 12 cross-border drivers from Hong Kong tested positive for the virus on Sunday, pushing the total number of drivers testing positive since Feb 4 to 35, authorities said.

Since Feb 7, Shenzhen authorities have required cross-border truck drivers from Hong Kong to show negative results for nucleic acid tests done in the past 24 hours when entering the city, and they are required to have samples collected at entry ports for another test.

During their stay in Shenzhen, they are required to undergo nucleic acid testing once a day.

Lyu Taobo, an executive from the transfer stations in Shenzhen's Baoan district, said truck drivers from Hong Kong can now park their vehicles in designated areas at the transfer stations.

Drivers are required to disinfect the cabs with cleaning products offered by the transfer station before they are allowed to leave for designated resting sites, while transfer station staff members are responsible for disinfecting the exteriors of vehicles and cargo, he said.

Mainland drivers are allowed to drive trucks to cargo transfer sites only after the trucks have been disinfected and ventilated for 15 minutes, he added.

Zou Shengqiang, who is in charge of COVID-19 prevention and control work at the transfer stations, said professional personnel have been sent to help manage the transfer stations and dormitories to prevent the spread of the virus, with waste at the transfer stations handled with the same care as medical waste.

Zou said that all staff members and drivers are required to show negative results for nucleic acid tests done in the previous 24 hours before they are allowed to enter the transfer stations.