"What turned the operation upside-down was some significant changes they made," said Gorny. "It was a very tragic alignment of poor facility design, poor design of equipment and very unique post-harvest handling practices of those melons. If any one of those things would have been prevented, this tragedy probably wouldn't have occurred."
But the story of what happened at Jensen Farms, and why no one stopped the sale and shipments of the cantaloupes, also sheds light on serious problems in the nation's fresh produce food safety net, and a voluntary system created by businesses to ensure a quality product, known as third-party audits.
Gorny and his team of experts from the FDA, the CDC, and other food safety experts would discover a multitude of problems at Jensen Farms, all tied to a series of changes that the Jensen brothers instituted in the packing shed on their farm just before the 2011 harvest.
The investigators said they found, among other things, a dripping, potentially contaminated condensation line allowing water to get onto the floor; water was pooling on the floor; sections of the floor had cut holes and jagged sides that were difficult to clean. Samples taken from the pooled water were positive for the Listeria that sickened people. On the rolling line where the melons moved, investigators found dirty equipment used to wash and dry the melons, and it could not be easily cleaned.
The FDA report stated that "several areas on both the washing and drying equipment appeared to be un-cleanable, and dirt and product buildup was visible on some areas of the equipment, even after it had been disassembled, cleaned, and sanitized." What's more, inspectors found that an older, secondhand washing machine designed for cleaning potatoes had been substituted to clean the melons.
"Because the equipment is not easily cleanable and was previously used for handling another raw agricultural commodity with different washing and drying requirements, Listeria monocytogenes could have been introduced as a result of past use of the equipment," the FDA report stated.
The equipment on the line, including rollers and pads that touched many melons as they passed by also yielded numerous positive genetic matches of Listeria, according to Gorny.
But there was also one other significant point, Gorny and many other food safety experts said. The change in procedures and equipment had also resulted in the removal of what had been used previously to decontaminate melons of bacteria; the farmers had removed their antimicrobial wash. Without it, melons that pass along the packing equipment and are placed in pools of water to rinse can cross-contaminate one another, and an entire production line can spread dangerous bacteria.
"That water can then become a source of contamination, so that if one bad melon gets into that system, you can imagine it can contaminate the water and basically contaminate every melon that comes after it," Gorny said.
The contaminated melons were shipped out and distributed across the country through an efficient system that took them to hundreds of supermarkets and retailers, and then into people's homes. The sick, the elderly and pregnant women were the most vulnerable.
Expert calls third-party audit system worthless
Since September, at least 30 people in the United States have died, many of them after suffering excruciating pain and some having gone into comas for weeks. One died as recently as March.
And every single death has been linked genetically to Jensen Farms, according to FDA investigators.
Although the CDC's official death toll stands at 30, CNN has confirmed death certificates giving Listeria as the cause in at least two other deaths linked to the outbreak. CDC officials say they plan to continue tracking victims and will update records later this year.
The cantaloupes, like much of the produce Americans eat, were not inspected by any government body. The reason is that the FDA simply does not have the money or the manpower to inspect all fresh produce on all farms. The agency is responsible for watching over some 167,000 domestic food facilities or farms, and another 421,000 facilities or farms outside the United States, according to FDA officials. But there are only about 1,100 inspectors to oversee these facilities, officials said.
In the absence of FDA inspectors, food retailers and the industry have created the third-party audit system, in which auditors are hired by farms or facilities to inspect their premises and provide scores.
But many food safety experts, and some members of Congress, have assailed the audit system, saying it is unreliable and full of conflicts of interest.
Just days before the Listeria outbreak, Jensen Farms paid a private food inspection company called Primus Labs to audit their operation. Primus Labs subcontracted the job to another company, Bio Food Safety, which sent a 26-year-old with relatively little experience to inspect Jensen Farms.
The auditor was James DiIorio, and he gave Jensen Farms a 96% score, and a "superior" grade. On the front page of his audit at the farm, DiIorio wrote a note saying "no anti-microbial solution" was being used to clean the melons.
Dr. Trevor Suslow, one of the nation's top experts on growing and harvesting melons safely, was shocked to see that on the audit at Jensen Farms.
"Having antimicrobials in any wash water, particular the primary or the very first step, is absolutely essential, and therefore as soon as one hears that that's not present, that's an instant red flag," Suslow said. The removal of an antimicrobial would be cause for an auditor or inspector to shut down an entire operation, he said.
"What I would expect from an auditor," Suslow said, "is that they would walk into the facility, look at the wash and dry lines, know that they weren't using an antimicrobial, and just say: 'The audit's done. You have to stop your operation. We can't continue.'"
The auditor, James DiIorio, did not return CNN's calls. The subcontractor, Bio Food Safety, and Primus Labs, declined CNN's interview requests. Eric and Ryan Jensen, the young farmers who changed their procedures, also declined an on-the-record interview.
To some food safety experts, the third-party audit system the Jensens relied on is a joke.
"These so-called food safety audits are not worth anything," said Dr. Mansour Samadpour, president and CEO of IEH Laboratories, one of the nation's largest food safety consulting labs for industry. "They are not food safety audits. They have nothing to do with food safety,"