Equipment that was corroded, dirty, and hard to clean may be to blame for the deadliest foodborne illness outbreak in years, according to an assessment by the Food and Drug Administration.

One-third of the samples taken by government investigators at the Jensen Farms cantaloupe-packing facility in September tested positive for listeria.

The FDA also noted the farm purchased the used equipment in July – which is also when the outbreak began. Tests revealed “widespread contamination throughout your facility and indicates poor sanitary practices in the facility,” the agency’s letter to the farm said.

Listeria-contaminated cantaloupe from the Colorado farm has been linked to 25 deaths in a dozen states. Jensen Farms recalled the tainted fruit in mid-September.

Listeria is especially harmful to the elderly or those with compromised immune systems. Most of the 123 people sickened in this outbreak are over 60 years old, according to the Centers for Disease Control and Prevention.

Although the number of new cases appears to be decreasing, listeria’s two-month incubation period means the number of illnesses may continue to grow.

“It’s too soon to declare the outbreak over," said Dr. Barbara Mahon of the CDC.