At least three national supermarket operators have decided to stop buying ground beef that contains the filler now known as "pink slime."

Federal regulators say the filler, known in the industry as "lean, finely textured beef," meets food safety standards. But critics say the product could be unsafe and is an unappetizing example of industrialized food production.

Supervalu Inc. — which operates owns stores under the Acme, Albertsons, Cub Foods, Farm Fresh, Hornbacher's, Jewel-Osco, Lucky, Shaw's/Star Market, Shop 'n Save and Shoppers Food & Pharmacy banners — said Wednesday that customer concern prompted it to stop carrying products containing the filler.

The Food Lion chain, owned by the Belgian Delhaize Group, also said Wednesday that it plans to stop carrying fresh ground beef with either of two similar fillers. Both are made with beef trimmings left over from other cuts. Spokeswoman Christy Phillips-Brown emailed a statement saying that the company is working with suppliers to make the change — and that the company guarantees the "80 percent lean ground beef" it already sells doesn't contain the fillers.

Food Lion also operates Bloom, Harveys and Reid's stores.

Safeway Inc., which operates the Genuardi's and Dominicks chains, as well as Safeway stores, said Wednesday that it also has announced it will stop selling fresh or frozen ground beef with the filler.

Public outcry over "pink slime" has grown sharply as images, media reports and online petitions about it have spread.

The low-cost additive, which has been used for years, is made from fatty bits of leftover meat that are heated, spun to remove the fat, compressed into blocks and exposed to ammonia to kill bacteria. Producers often mix the filler into fattier meat to produce an overall leaner product and reduce their costs.

The U.S. Department of Agriculture announced this month that, beginning in the fall, the National School Lunch Program will let school districts decide whether to buy ground beef that contains the filler. Previously, it was difficult for schools to know whether beef they bought from the feds had it or not.

As a result, a number of schools have said they will stop using meat with the controversial filler.

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Celebrity chef Jamie Oliver has spoken out against it, and fast-food chain McDonald's Corp. decided last year to stop putting ammonia-treated meat in its products.

Shares of Supervalu, which is based in Eden Prairie, Minn., fell 7 cents to close at $6.20 Wednesday and rose 3 cents in after-hours trading.