The government chose not to alert the public about suspect ground beef or request a recall after a 2004 salmonella outbreak in several states, including Colorado.
That's according to the Centers for Disease Control and Prevention.
The outbreak sickened at least 31 people nationwide.
The report was made public by food safety advocates.
It says the Agriculture Department traced illnesses in nine states to a national supermarket chain and a single meat processing plant.
The affected states were Colorado, Kansas, Minnesota, New Jersey, New Mexico, New York, Ohio, Tennessee and Wisconsin, and Washington, D.C.
Salmonella in raw meat is not an "adulterant" under federal guidelines.
That's because people are expected to cook raw meat before they eat it, and cooking kills salmonella.