The criminal division of the Food and Drug Administration (FDA) and the Justice Department have joined the probe of the Iowa farm at the heart of the recent egg recall linked to an outbreak of salmonella, FDA Commissioner Margaret Hamburg said Wednesday.

"There is a formal investigation going on that extends beyond the FDA inspections that are focused on farm practice," said Hamburg during a press conference at the Justice Department on an unrelated matter.

"It is the case that an investigation is underway," she said. "We are pursuing it with our partners in law enforcement."

Hamburg declined to discuss details or say whether Federal Bureau of Investigation (FBI) agents visited facilities of Wright County Egg, a major egg producer that recalled 380 million eggs in mid-August.

Wright spokeswoman Hinda Mitchell said FDA officials were there Tuesday and she said she believed FBI agents were also present.

A Justice Department spokeswoman declined to comment.

Some 1,470 cases of salmonella have been reported to federal health authorities since late spring.This week the FDA said that the strain of salmonella found in the patients was identified in samples of Wright's chicken feed and in a few places on the farm.

It released a report detailing numerous sanitation problems at Wright County Egg and its parent company Quality Egg, which makes feed for Wright and another company involved in the recall, Hillandale Farms of Iowa.

Hamburg said the agency is working with the companies "to make sure that they clean up the subpar practices, that eggs do not go back into the marketplace that are not safe and that we continue to make sure that there aren't further recalls that might need to be taken in order to fully ensure that the public is protected."

Wright said it is cooperating with the FDA and had already fixed many of the issues that were identified.

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