One of the world’s busiest ports could see shipments delayed as a Covid-19 outbreak that earlier closed part of the facility spurs stricter virus-control measures.

All cargoes leaving Yantian Port in China will require reservations, according to a port employee, who declined to be identified as they’re not authorized to speak to the media. The port has strengthened its Covid-19 testing program for imports and cargoes into China could also be delayed, the employee said when asked whether vessels arriving at the port could be interrupted.

Yantian Port in the export and industrial hub of Shenzhen in southern China had temporarily stopped accepting containers for export until Sunday May 30, according to a notice posted Friday on Wechat. The container yard of the port has been partly shut since last week after an outbreak of Covid-19 among port staff and in the broader community, state media reported.

Yantian is one of the busiest ports in the world, with a cargo throughput of 13.34 million twenty-foot equivalent unit in 2020, a standard measurement used in freight industry, according to figures from the Shenzhen Transportation Bureau. It serves about 100 ships a week, according to a report on a Shenzhen government website.

Shares of Shenzhen Yan Tian Port Holding Co., the operator of the port, slid as much as 1.8% on Monday. Calls to the company’s offices went unanswered.

The disruptions will continue into the coming week, with shipping firm AP Moller-Maersk A/S reporting delays in its schedules due to the closure. Any delays will likely put further pressure on the already sky-high costs of shipping goods from China, which have soared on record export demand, a shortage of containers, and other factors.

Those shipping costs are just one of the factors boosting the price of China’s exports, which are threatening to further fuel global inflation.

The local government said in a notice Friday it will conduct mass testing of the entire population of the Yantian district.