The deadly listeria outbreak in cantaloupe was probably caused by old, hard to clean packing equipment at a Colorado farm, the Food and Drug Administration said Wednesday.
The deadliest outbreak of foodborne illness in more than 25 years claimed 25 lives as a result of the contamination.
The Centers for Disease Control and Prevention said 123 people were also sickened in the outbreak.
The farm had recently purchased used equipment that was corroded, dirty and hard to clean. The packing facility floors were also difficult to clean, allowing pools of water potentially harboring the bacteria to form close to the packing equipment.
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The new revelations are included in the FDA's six-page assessment of the conditions at the farm and are based on investigators' visits in late September.
The equipment -- purchased in July, the same month the outbreak started -- was previously used for a different agricultural commodity, the agency said, and the listeria "could have been introduced as a result of past use of the equipment," according to the report.
The FDA said that samples of cantaloupes in Jensen Farms' fields were negative for listeria, but bacteria coming off the field may have initially introduced the pathogen into the packing house, where it then spread.
Listeria contamination often comes from animal feces or decaying vegetation.
The report also cited another possible source of contamination -- a truck that frequently hauled cantaloupe to a cattle operation and was parked near the packing house.
Contamination could have been tracked into the house by people or equipment, according to the FDA.