(Bloomberg) -- A suspension of trucking services in several parts of East China’s Zhejiang province has slowed the transportation of manufactured goods and commodities through one of the world’s most important ports.

There are strict controls on trucks transporting goods to or from the Beilun district in Ningbo after the discovery of several cases of Covid-19 in the area, shipping line AP Moller-Maersk A/S said in a Thursday customer advisory. This suspension, along with restrictions on truckers in some areas in and around Zhejiang, has halted operations at some yards and warehouses at Ningbo port.

The restrictions began last week after the city reported an outbreak of Covid-19 which led to the closure of schools, warehouses, and companies in the Beilun district near to the port. The first reported infection was an employee of clothing company Shenzhou International Group, and the outbreak is concentrated in that company’s factory, according to the Global Times newspaper. 

Ports around the world have been struggling to ease congestion as the pandemic heads into a third year. Ningbo is one of the world’s top container ports and a crucial part of the global supply chains that connects factories in East China to consumers of automobiles, machines, electronics and toys in the U.S., Europe and elsewhere. 

The port was partly shut for weeks last August after a Covid-19 outbreak, causing a slowdown in exports, disruptions and congestion across supply lines. 

Read more: Port Shutdown Goes Beyond China to Upset Trade and Supply Chains

China’s policy of swift and extensive lockdowns in response to even small outbreaks has repeatedly stopped the domestic spread of Covid-19, saving lives and also allowing companies to continue to produce and export. But it has also led to supply-chain congestion and taken a toll on mariners and the shipping industry. 

Some polyester factories in Ningbo have stopped work as they can’t receive raw materials via truck or ship out goods, according to analysts at Wood Mackenzie Ltd. Road deliveries of liquefied natural gas, an important fuel for industries unconnected to pipelines, has also slowed, said the analysts.

ENN Energy Holding’s liquefied natural gas terminal on Zhoushan island resumed truck shipments earlier this week and local officials are also allowing more trucks to pick up gas from Cnooc Ltd’s terminal at Ningbo port. However, total volumes are far below the 300 to 400 trucks that normally take gas from the port each day, according to Sun Xuelian, an analyst at consultant JLC. 

About 10% of trucking capacity in the Ningbo area has recovered, while 20% of drivers are estimated to have been permitted by authorities to resume services, according to Maersk.

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