Small pieces of metal have been found in at least 200 bottles of acetaminophen pain pills nationwide.

The affected pills are made by Perrigo, which bills itself as the world's largest manufacturer of store-brand nonprescription drugs, and are sold under private labels by retailers including Wal-Mart, CVS, Safeway, and SuperValu.

The FDA designated the recall voluntary because the problem poses only a temporary health risk, and the chance of serious injury is remote.

Persons who ingest contaminated pills could potentially suffer minor stomach discomfort or cuts to the mouth and throat, and they should consult a doctor, the FDA advises. No immediate reports of injuries or illness have been reported.

Perrigo did a quality-control check of acetaminophen pills after learning that their equipment was wearing down prematurely. Metal was detected in approximately 200 of the 70 million tablets screened.

Some of the caplets were made as long as three years ago, with expiration dates ranging from September 2006 to August 2009, FDA officials said.

Perrigo said the pills contained raw material purchased from a third-party supplier and affected 383 batches. Perrigo hasn't stated where the contaminated pills were made. Its main factories are in the U.S. and Israel, with secondary plants in the United Kingdom, Mexico, Germany and China.

Perrigo has carried out at least 32 other product recalls since 1993, according to FDA records. Sources indicate that this was Perrigo's 11th recall for the year and its 23rd since 2001.

As recently as May, 2006 it recalled nearly 59,000 bottles of a 500-milligram combination pain reliever and sleep aid due to contamination with acrylic mirror particles.

A list of recalled lot numbers is available on the FDA's website, fda.gov. Consumers seeking more information can also call Perrigo's recall hot line, 877-546-0454.