U.S. automaker Tesla is suspending production at its Shanghai factory for four days after the financial hub said on Sunday it would implement a temporary closed-off management to carry out mass testing for COVID-19, Reuters reported, quoting two people familiar with the matter.

The company has notified its workers and suppliers of the move, the sources said. It initially attempted to create a closed loop to continue production and called workers in on Sunday, one of the sources said. However, it allowed them to leave that evening after it decided it did not have enough provisions for them, the source added.

Bloomberg News reported on Sunday that the company will halt production for at least one day, citing people familiar with the matter.

Tesla declined to comment on whether production had been suspended. In a statement to Reuters, it said that it always endeavored to fulfill its epidemic prevention responsibilities and that it believed Shanghai's COVID-19 measures helped lay the foundation for the city's future development.

Two-phased closed-off management and a new round of nucleic acid testing for residents were launched in Shanghai on Monday morning.

The enforcement is carried out using Huangpu River that runs through the city as a guide. Regions lying to the east and south of the Huangpu River, including Pudong and its adjacent areas, were first to be put under such management from Monday till early Friday morning. Then urban districts west of the Huangpu River will start mass testing under closed-off management from April 1 to 5. 

The Tesla factory locates in Lingang in Pudong New Area, which is part of Shanghai's first phase of closed-off management.

The factory has already had a halt of production for two days in mid-March after the city rolled out strict movement controls and carried out mass testing to curb the rising number of COVID-19 cases.

The plant is key to Tesla's delivery in China and export to Germany and Japan. It delivered 56,515 vehicles in February, including 33,315 for export, according to the China Passenger Car Association.

That amounts to an average of about 2,018 vehicles a day.

(With input from Reuters)