Austin "Jack" DeCoster and his son, Peter DeCoster, are scheduled to testify before a House Energy and Commerce subcommittee Wednesday. The panel has asked them to come prepared to explain what steps they have taken to address salmonella contamination found at their farms.

In testimony released by the Iowa-based company, Wright County Egg, the two men say they believe an ingredient sold to them by an outside supplier may be to blame for the outbreak.

So far, an investigation by the federal government's regulatory Food and Drug Administration appears to be focused on Wright and another company linked to the illnesses, Hillandale Farms. The two companies recalled more than a half billion eggs related to the outbreak in August.

Agency investigators found several samples of salmonella at the two farms, along with towers of manure and bug and rodent infestations. An investigation by the House subcommittee found that Wright County Egg had received hundreds of positive results for salmonella in the two years before the outbreak.

The president of Hillandale Farms, Orland Bethel, will also testify at the hearing. Wright County Egg operates one of Hillandale's barns and supplies feed to the company.

The specific cause of the outbreak is still unknown, and the FDA is still investigating.

No deaths have been reported due to the outbreak. The federal Centers for Disease Control and Prevention has said this is the largest outbreak of this strain of salmonella since the start of the agency's surveillance of outbreaks in the late 1970s. For every case reported, there may be 30 that are unreported.