Smithfield Foods Inc. said it would close two more pork-processing plants because of the coronavirus pandemic, reducing meat supplies for grocery stores and deepening challenges for farmers.

The top U.S. pork processor said it would close plants in Wisconsin and Missouri later this week, after announcing Sunday the shutdown of its Sioux Falls, S.D., plant, one of the industry’s biggest. Smithfield said that employees at all three plants have tested positive for the coronavirus and that the Missouri plant needed pork supplies from the South Dakota facility to operate.