The U.S. Food and Drug Administration has found that the deadly listeria outbreak in cantaloupe that killed 25 people was probably caused by packing equipment and pools of water on the floor near equipment and employee walkways at Jensen Farms in Colorado.

An FDA assessment of conditions at the farm found that Jensen Farms had recently purchased packing equipment that was not easily cleaned and sanitized. The equipment had been previously used in potato production, an FDA adviser said.

“This was brought into the facility, part of a new practice,” Sherri McGarry told reporters on a background conference call.

The floors of the packing facility were also hard to clean, so pools of water that could have harbored bacteria were close to equipment at Jensen Farms.

During an investigation of the facility, the FDA found a truck used to haul culled cantaloupe that parked adjacent to the packing facility could have introduced contamination into the facility.

The FDA also found that the growth of listeria monocytogenes could have occurred as the result of how the cantaloupes were cooled after coming off the fields. Jensen Farms told the FDA it did not pre-cool its cantaloupe to remove condensation before cold storage. Pre-cooling is used to remove the heat in cantaloupes to protect them from bacterial growth.

McGarry said the investigation of Jensen Farms near Holly, Colo., is still on-going so there is additional information the FDA has found that it cannot share.

Jensen Farms agreed earlier this week to FDA inspections of its growing, packaging and cold storage operations before it resumes food harvesting, packaging or processing. The company also say it will correct all concerns noted during the FDA inspections.

“The tragic illnesses from this outbreak have again demonstrated the need to continually address and improve food and safety practices, and the need to have a system based on prevention so that this type of tragedy does not happen again,” FDA Commissioner Margaret Hamburg said.

Health officials continue to monitor the outbreak, which is the deadliest food-borne outbreak in the United States in more than 25 years. There have been 123 cases, and 25 deaths, in 26 states.

Dr. Barbara Mahon, a deputy branch chief of enteric diseases at the CDC, said, “It’s too soon to declare the outbreak over. We’ll need to monitor for at least another two weeks to see whether the number of cases goes back to the baseline.”

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