Millions of bottles of the pain reliever acetaminophen are being recalled because they may contain metal fragments.

The recall affects 11 million bottles containing varying quantities of 500-milligram acetaminophen caplets made by the Perrigo Co. The pills were sold under store brands by Wal-Mart, CVS, Safeway and more than 120 other major retailers, the Food and Drug Administration said, some as long ago as three years. At least two chains - CVS Corp. and SuperValu Inc. started pulling the pills from store shelves Thursday.

According to the FDA, the pills included metal fragments (though the type of metal has yet to be determined),ranging in size from microdots to portions of wire one-third of an inch long.

The discovery was made during quality-control checks done after the company Perrigo, discovered its equipment was wearing down prematurely, the FDA said. Agency officials declined to say whether the metal found in the pills caused the damage or resulted from it.

According to the FDA, a company investigation turned up metal in about 200 of the 70 million pills it passed through a metal detector.

Consumers who take any of the contaminated pills could have minor stomach discomfort or possible cuts to the mouth and throat, the FDA said, adding that the risk of serious injury was remote, and as of yet there has been no immediate reports of ilness.

Acetaminophen is best known as the drug in products sold under the Tylenol brand, but it is available in typically less expensive generic versions. Acetaminophen along with aspirin and ibuprofen, is one of the most popular pain relievers available over the counter.

The recall does not affect Tylenol. Nor should the recall cause a shortage of acetaminophen, the FDA said.

Perrigo says it is the world's largest manufacturer of store-brand nonprescription drugs. The retail market for the pain relievers is worth more than $2 billion a year.

Kevin Vincent, 44, of Arlington, Va., said "If it's not something that has any chance of recurring, then I really wouldn't worry."

The 129 retailers that could potentially be affected by the recall include Wal-Mart Stores Inc. CVS, Safeway Stores and SuperValu as they sell the Perrigo-made pills under their own or other private labels.

CVS will stop selling its own brand of 500-milligram acetaminophen caplets and pull bottles from store shelves nationwide. SuperValu also began removing the pills from its Albertsons, Cub Foods and other stores, according to their spokespersons.

Molly Walsh, 21, a George Washington University student shopping at a CVS pharmacy in Washington, said she did not plan to toss any of the store-brand drugs at home, "It's still going to be cheaper and I'm still going to be broke after the recall."

The FDA did not know in which states the pills had been sold, but recommended that customers determine whether products they bought are being recalled by checking the store list on the FDA Web site, and the batch list. The batch numbers appear on the container's label.

It has not been determined where Perrigo made the pills. Its main factories are in the United States and Israel, with secondary plants in the United Kingdom, Mexico, Germany and China.

According to FDA records, Perrigo has carried out at least 32 other product recalls since 1993, as recently as May when it recalled nearly 59,000 bottles of a 500-milligram combination pain-reliever and sleep aid that contains acetaminophen because of contamination with acrylic mirror particles.