The U.S. Food and Drug Administration released the "Report on Factors Potentially Contributing to the Contamination of Fresh, Whole Cantaloupe Implicated in the Multi-State Listeria Monocytogenes Foodborne Illness Outbreak," which said there could have been low-level sporadic listeria monocytogenes in the field where the cantaloupe were grown in Colorado.
It is also possible a truck used to haul culled cantaloupe to a cattle operation was parked adjacent to the packing facility and could have introduced contamination into the packing house, the report said.
Once introduced into the packing facility, listeria may have spread by:
-- The packing facility's design allowed water to pool on the floor near equipment and employee walkways.
-- The packing facility floor was constructed in a manner that made it difficult to clean.
-- The packing equipment was not easily cleaned and sanitized; washing and drying equipment used for cantaloupe packing was previously used for post-harvest handling of another raw agricultural commodity.
Listeria may have grown because there was no pre-cooling step to remove field heat from the cantaloupes before cold storage. Therefore, the cantaloupes cooled there may have been accompanied by condensation that promoted the growth of listeria monocytogenes, the report said.
FDA officials said they issued a warning letter to Jensen Farms, where the cantaloupes were grown, based on environmental and cantaloupe samples collected during an inspection. However, FDA's investigation at Jensen Farms is still considered open, FDA officials said.