The U.S. attorney's office in Newark, New Jersey has taken over a criminal investigation of quality control problems at Schering-Plough Corporation's Puerto Rico manufacturing plant. Officials with a branch of the U.S. Food and Drug Administration (FDA) in the territory were previously heading the investigation. A report in Wednesday's Newark Star-Ledger revealed that the facility may have used chemical products in its drug manufacturing process that were not approved by the FDA.

The investigation extends from a February 2001 FDA inquiry that found manufacturing procedures at Schering's New Jersey and Puerto Rico plants did not meet government standards. In May, as part of a consent decree with the government, Schering agreed to pay $500 million to settle the FDA complaints. The drug maker is best known for the allergy medications Claritin and Clarinex.