WASHINGTON - Federal agents searched facilities of a dog- and cat-food manufacturer and one of its suppliers as part of an investigation into the widening recall of pet products, the companies disclosed yesterday.

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 companies said.

Menu Foods made many of the more than 100 brands of pet food recalled since March 16 because of contamination by the chemical melamine. ChemNutra supplied the manufacturer with wheat gluten, one of the two ingredients tainted by melamine used in recalled pet products. Both companies said they were cooperating with the investigation.

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 food is a misdemeanor.

The FDA also is looking at all other ingredients imported by ChemNutra, and trying to reconcile what it imported with what it supplied to customers, an agency spokeswoman said.

Meanwhile, the FDA asked American Nutrition Inc. to voluntarily recall pet foods it had manufactured for independent companies using rice protein imported from China by Wilbur-Ellis Co. ANI's own brands are not part of the recall, the company said in a statement.

Several of the companies recalling food contend in statements on their Web sites that ANI added the rice protein concentrate without their knowledge or approval.

On Thursday, the Utah Department of Agriculture and Food announced that about 2,500 hogs from four farms would be euthanized because they may have eaten contaminated pet-food scraps from ANI. The FDA had decided that any animal that might have consumed feed from the plant after April 1 should be euthanized as a precaution.

An unknown number of dogs and cats in the United States have been sickened or died after eating chemical-laced pet food.

Menu Foods said it faced more than 50 lawsuits. It, in turn, has sued ChemNutra.

Read detailed pet-food recall updates via http://go.philly.com/health