Federal health officials have begun a criminal investigation into the actions of the Peanut Corporation of America, which they said knowingly sold contaminated peanut butter and peanut products to major food makers.

The investigation is being conducted by the Food and Drug Administration and the Justice Department, according to Dr. Stephen F. Sundlof, director of the food center at the F.D.A.

The agency rarely discloses criminal investigations that are in progress, but did so in this case after several influential members of Congress demanded a criminal investigation in recent days.

The contamination of the company’s products with salmonella bacteria has led to one of the largest food recalls in the nation’s history. More than 400 products containing peanuts, peanut butter or peanut meal have been recalled, and more recalls are expected.