OMAHA — ConAgra Foods, Inc. said it is undertaking an “indefinite shutdown” of its potato processing plant in Prosser, Wash., on May 30. The closing is expected to affect 250 workers at the plant.

“The plant’s shutdown comes as a result of current economic conditions that have softened market demand for frozen potato products — something our entire industry is experiencing,” said Jeff Mochal, director of corporate communications for ConAgra. “The Prosser plant is also our highest cost plant to operate. As demand for our products decreased, it was necessary to discontinue operations at this facility.”

The Prosser plant, which was acquired by ConAgra in 2007 from Twin City Foods, is part of the ConAgra Foods Lamb Weston Commercial Foods business. The plant makes a variety of frozen potato products sold mainly within retail and food service.

Mr. Mochal said the Prosser plant is one of several Lamb Weston facilities in the area. The company also operates sites in Pasco, Wash.; Richland, Wash.; Hermiston, Ore.; and Boardman, Ore.