U.S. Attorney General Eric Holder said on Friday his office was concerned about the massive egg recall from the Iowa farms but would not comment if his office was considering opening an investigation.

I am very concerned about what I have read regarding the production of these eggs, Holder said. We are determined to make sure that we protect the American people from these kinds of things and to prevent them from happening in the future.

Holder spoke during a press conference held in Fort Collins, Colorado, in conjunction with a joint U.S. Agriculture Department/Department of Justice workshop examining competition in the livestock industry.

The U.S. Food and Drug Administration said it has linked a bacteria found in chicken feed used at two Iowa farms to the salmonella outbreak that prompted the recall of more than a half billion contaminated eggs.

The contaminated feed was produced at a feed mill that is part of Wright County Egg operation and also went out to the second farm linked to the outbreak, Hillandale Farms of Iowa, FDA said.

The outbreak, largest since the 1970s, may be linked to almost 2,400 cases of salmonella-related illnesses around the country since May 1, although at least 930 such cases are reported during this time frame on an average year.