"There was gross negligence and malfeasance at best, maybe even complicity involving USDA personnel," Huffman said.
In the aftermath of the recall, reports surfaced of improper relationships involving USDA Food Safety and Inspection Service (FSIS) inspectors and employees at the slaughterhouse. But any role the inspectors played in contributing to the recall was not revealed in the criminal case.
"Here we are two years later without any information on the internal investigation that should have happened, should have been concluded by now," Huffman said.
The recall prompted an investigation by the USDA's Office of the Inspector General (OIG), which helped the U.S Attorney's Office in its prosecutions.
Huffman says the agency's inspector general has "provided us with no information about that and we've continued to press."
"USDA did a sweeping recall that captured headlines and sort of diverted public attention away from the misconduct and the failures of its own personnel," Huffman said. "This is part of the story that has to be told."
A USDA OIG official did not respond to a request for comment.
But the USDA itself emphasizes that it's not to blame.
"The criminals who are solely responsible for the events at Rancho are appropriately facing justice," said Adam Tarr, chief of staff at the USDA's Office of Food Safety, in an emailed statement. "The U.S. Attorney's Office conducted a thorough investigation and found no criminal wrongdoing on the part of USDA's inspectors."
"It is dangerous and contrary to the facts of the case to suggest otherwise," Tarr said. "The defendants in this case knowingly and willingly took steps to avert USDA inspection."
A food safety advocate who has tracked the federal government's response to the recall wants to know what the agency has done to improve its inspections since 2014.
"I'm still concerned on the USDA side that not enough has been done to fill in the loopholes of the inspection process," said Tony Corbo, a senior lobbyist at Food & Water Watch. "What's the USDA done on its end to prevent similar circumstances from happening in the future?"
Last July, federal officials revealed the measures they intend to take to improve meat safety inspections because of the recall. The USDA's top food safety official then said the agency was hiring 32 full-time inspectors at "high-risk" meat processing plants around the country.
But the union that represents meat inspectors filed an unfair labor practice charge, blocking the hiring over concerns the new workers would not be protected from severe temperatures in holding pens.