Other manufacturers say the Chinese government is still claiming all the masks that their factories in the country make. “Mask exports are still not authorized, but we are following the situation every day,” said Guillaume Laverdure, chief operating officer of Medicom, a Canadian manufacturer that makes three million masks a day at its Shanghai factory.

Much as it dominates manufacturing of cars, steel, electronics and other necessities, China is essential to the world’s supply of protective medical gear. Most of what it makes are the disposable surgical masks worn by health professionals. It makes a smaller number of N95 respirator masks, which provide more filtration for doctors and nurses.

The general public does not need to wear masks, according to the U.S. Centers for Disease Control and Prevention. But demand for surgical masks has skyrocketed in China, where the police require anyone who goes out in public to wear a mask.

Though companies say China is claiming virtually all mask output, the Chinese government said it had never issued a regulation prohibiting mask exports and was willing to work with other countries to share.