The U.S. Department of Agriculture says the vast majority of states participating in its National School Lunch Program have opted to order ground beef that doesn't contain the product, known in the industry as lean finely textured beef.

Only three states — Iowa, Nebraska and South Dakota— chose to order ground beef that may contain the product.

The product has been used for decades, and federal regulators say it's safe to eat. It nevertheless became the center of national attention after the nickname "pink slime" was quoted in a New York Times article on the safety of meat processing. The filler is made of fatty bits of beef that are heated to remove much of the fat, then treated with a puff of ammonia to kill bacteria.

In response to the public outcry over its use, the USDA said in March said that it would for the first time offer schools the choice to purchase beef without the filler for the 2012-2013 school year. The department has continued to affirm that lean finely textured beef is a safe, affordable and nutritious product that reduces overall fat content.

But as of May 18, the agency says states ordered more than 20 million pounds of ground beef products that don't contain lean finely textured beef. Orders for beef that may contain the filler came to about 1 million pounds.

Because schools were not given a choice last year, all states may have previously received beef with the product.

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The agency is still accepting orders for the upcoming school year.

The USDA does not buy lean finely textured beef directly, but buys products from beef vendors who must meet the agency's specifications; ground beef can include no more than 15% of the product.

The USDA's National School Lunch Program buys about 20% of the products served in schools across the country; the rest is bought by schools or school districts directly through private vendors.

The percentage of beef that schools get through the USDA tends to be higher, however, because beef is expensive and schools like to take advantage of favorable prices the government can negotiate.

Schools aren't the only ones rejecting the product. In the wake of the public outcry, fast food chains and supermarkets have also said they would stop selling meat that includes lean finely textured beef.

Beef Products, the South Dakota company that makes lean finely textured beef, has been hurt by the controversy about its product. This month, the company announced it will shut three of its four plants.