Tesla suspended production at its busiest facility in Shanghai, according to an internal memo.

No reason was given for the work stoppage, according to Reuters, whose reporters saw the communication. It simply told the morning shift workers they could start their holiday break early.

Earlier this month, Elon Musk’s electric vehicle manufacturer said that it was stopping work ahead of the holiday break, but the expected shutdown came earlier than announced.

Tesla had planned to suspend production of Model Y vehicles from Dec. 25 to Jan. 1.

The work stoppage comes amid a surge in COVID infections in China. Workers have been calling in sick at the plant, according to the news service.