Patty Lovera, assistant director of Food and Water Watch, a non-profit consumer group, said the USDA argument that it was not its job to enter hen houses technically was correct.
"It's a little sad that they [the USDA] can't pick up a phone and call the people whose job it is to investigate this," she said. "They know it's the FDA's job. They could have called them. They could have blown the whistle and, hopefully, speeded up this process before people got sick."
In a statement today, Agriculture Secretary Tom Vilsack said the "USDA has been working to close gaps and improve the safety of the meat, poultry and processed egg products over which we have authority and the FDA is taking action to address the fact that they have not had all of the tools needed to prevent outbreaks in areas where they have authority, such as shell eggs. "
The Arnolds said there were a lot of good egg producers following the rules.
"DeCoster [the owner of Wright County] is so huge in the business that it's hard to control a lot of it," he said.
In a statement today, Wright County Eggs said, "Anytime there is a perceived issue on our farm, we expect our employees to immediately bring it to our attention, so that we may address it appropriately and swiftly. That is our policy, and that is their responsibility. To the best of our knowledge, no concerns were ever raised."
The owners of Hillandale and Wright County have been asked to testify before Congress later this month.
ABC News' Chris Bury and affiliate KCRG in Cedar Rapids, Iowa, contributed to this story.