Demand for cans in the pandemic, caused mostly by a surge in sales of beer and other beverages, has increased to the point wher U.S. can manufacturers are having to import stock to keep up.

Retail sales of aluminum beverage cans went up almost 24% in March, and sales of canned food rose about as much in the first six months of this year. Molson Coors, Coca-Cola and other major can users are struggling to keep enough aluminum cans in stock, they told the Wall Street Journal.

The closing of bars and restaurants due to the pandemic shifted the demand for beer packaging from kegs to cans, as people started drinking at home. The advent of hard seltzer also helped spike demand.

Ball Corp. and Crown Holdings, America’s two largest aluminum can manufacturers, both told the Journal that they have been importing billions of cans from Europe, Brazil and other locations. Ball is about to bring two new production lines online, and the Can Manufacturers Institute says U.S. manufacturers should be able to produce 12 billion more cans by the end of 2021.