WASHINGTON -- Check your medicine cabinet: Millions of bottles of the widely used pain reliever acetaminophen -- some sold as long as three years ago -- 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 of Allegan, Mich. The pills were sold under store brands by Wal-Mart Stores Inc., CVS Corp., Safeway Inc. and more than 120 other major retailers, the Food and Drug Administration said. At least two chains -- CVS and SuperValu Inc. -- started pulling the pills from store shelves Thursday.

There were no immediate reports of injuries or illness. The contaminated pills included metal fragments ranging in size from "microdots" to portions of wire one-third-of-an-inch long, the FDA said. The FDA could not describe further the type of metal.

Perrigo discovered the metal bits during quality-control checks done after the company 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.

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

Consumers who take any of the contaminated pills could have minor stomach discomfort or cuts to the mouth and throat, the FDA said, adding that the risk of serious injury was remote.

Acetaminophen is best known as the drug in products sold under the Tylenol brand. But it is available in typically less expensive generic versions. The drug, along with aspirin and ibuprofen, is one of the most widely used pain relievers available without a doctor's note.

The recall does not affect Tylenol. Nor should the recall cause a shortage of acetaminophen, the FDA said. The FDA posted the recall batch numbers and the list of retailers on its website, www.fda.gov/bbs/topics/NEWS/2006/NEW01507.html.

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

The 129 retailers that could potentially be affected by the recall include Wal-Mart, CVS, Safeway and SuperValu. They typically 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, spokesman Mike DeAngelis said. SuperValu also began removing the pills from its Albertsons, Cub Foods and other stores, spokeswoman Haley Meyer said.