WASHINGTON - Federal agents searched facilities of a pet food manufacturer and one of its suppliers as part of an investigation into the widening recall of products made with ingredients contaminated by an industrial chemical, the firms disclosed Friday.

Food and Drug Administration officials searched an Emporia, Kan., pet food plant operated by Menu Foods and the Las Vegas offices of ChemNutra Inc., the supplier of one of two ingredients suspected in the contamination of millions of cans of recalled dog and cat food, according to the companies.

Menu Foods also said the U.S. Attorney's offices in Kansas and the western district of Missouri have targeted the company as part of misdemeanor investigations into whether it violated the federal Food, Drug & Cosmetic Act. The sale of adulterated or contaminated food is a misdemeanor. A Justice Department spokeswoman had no immediate comment.

“Menu Foods has been doing everything it can to cooperate with the FDA,” company chief executive officer Paul Henderson said in a statement. “Even before commencement of this investigation we have given the FDA full access to our plant and our records, have answered questions and provided documents to them any time they have asked.”

FDA spokeswoman Julie Zawisza would not confirm or deny that a search warrant was executed. “We have a strict policy of not discussing activities of our Office of Criminal Investigations,” she said.

ChemNutra said it had been informed the company could be held accountable because it imported the melamine-adulterated wheat gluten used in the tainted pet food even though the company had no knowledge that its Chinese supplier had introduced melamine into the product.

“We have cooperated and complied fully with FDA investigators both prior to and since being served with today's search warrant, and will continue to do so,” Steve Miller, chief executive officer of ChemNutra, said in a statement. “We keep very good records, which has made it relatively easy for the investigators to retrieve what they needed.”

ChemNutra spokesman Steve Stern said FDA agents arrived at the company's offices in the late afternoon and stayed until late in the evening. They copied computer hard drives, Stern said, adding, “we complied completely with the FDA.”

Menu Foods Midwest, an affiliate of Menu Foods, the company that last month recalled 60 million cans of pet food, earlier this week filed a lawsuit that seeks to have ChemNutra pay the costs of the recall plus damages.

ChemNutra maintains Menu Foods waited several weeks before notifying it about the problem. ChemNutra also says Menu Foods had other suppliers of wheat gluten.

Menu Foods, based in Streetsville, Ontario, recalled its products after 16 pets, mostly cats, died from eating contaminated food. Other manufacturers continue to recall pet food, with the FDA announcing the latest Friday.

The lawsuit, which lists Menu Foods Midwest, Menu Foods Ltd., Menu Foods Holdings Inc. and Menu Foods Inc. as plaintiffs, accuses ChemNutra of breach of contract and breach of implied warranties about the safety of the wheat gluten and its fitness for use in pet food. It said each shipment of wheat gluten came with a certificate saying it met Menu Foods' requirements.

“ChemNutra knew that Menu Foods was relying on ChemNutra's skill and judgment to supply high-quality wheat gluten,” the lawsuit said.

Menu Foods said it faces more than 50 lawsuits.