Mixing raw nuts with roasted ones -- a major "don't" when it comes to food safety -- is believed to be the problem behind the latest nut recall, Food and Drug Administration assistant commissioner for food safety David Acheson told ABC News today.
Acheson said that's the working theory behind new salmonella concerns that have prompted the recall of 2 million pounds of pistachios already distributed nationwide from California-based Setton International Foods, Inc.
"We've learned that on some of the lines, the firm had passed both raw and roasted pistachios, and so the possibility of cross contamination -- so that is the working hypothesis," Acheson said.
The latest salmonella worries come separate from an enormous ongoing peanut recall. Taken together, the recalls mean shoppers have slim pickings today when it comes to eating nuts.
At this early stage in the investigation, health officials are warning consumers to stay away from all pistachios.
"We don't know where these pistachios have gone right now," Acheson said. "What we do know is there is a million-plus pounds of pistachios that are out there somewhere."
After announcing the recall Monday night, the FDA spent today collecting the names of the 36 companies to whom the company at the heart of the investigation sold pistachios. The FDA is beginning the slow process of contacting those who received bad pistachios to figure out where the nuts went from there.
The bad pistachios are believed to be coming from the second largest pistachio producer in the country, Setton International Foods, in Terra Bella, Calif. The FDA and the California Department of Health have been inspecting and investigating the facility for the past few days.
Concerns about bacteria-tainted pistachios surfaced when Kraft Foods tested them as part of a routine analysis and "found a variety of different types of salmonella."
Acheson said today the investigation has so far found that the California plant was also testing its nuts, and did, on occasion, find salmonella.
As a result, he said they put the nuts back through their roaster. The roasting process is supposed to kill the bacteria, provided the machine is roasting properly.
"They had found some positives, and what they did with that was essentially put them back through the roasting process to ensure that any residual salmonella was taken care of," Acheson said.
"They are not obligated to tell FDA or anyone else if they've done that," he added.
Acheson also told ABC News he believes the company did not do subsequent additional tests to ensure the product was safe. He added that even if they did, one negative does not mean a batch is free and clear of the bacteria.
The FDA has announced the recall in advance of any confirmed illnesses. There have been some consumer complaints, but that doesn't mean definitively that the pistachios caused the illnesses.
"The good news is that the government is acting in advance of any illnesses. This means that, in fact, they are being more proactive to protect the public," Caroline Smith DeWaal, food safety director for the Center for Science in the Public Interest, told ABC News today.
The pistachio company at the focus of the investigation packs the nuts in large volume -- about 1,000 to 2,000 pounds of pistachios in each container -- and ships them to some three dozen suppliers and wholesalers that then repack or resell them to many other manufacturers under different brand names.
One of those companies was Kroger, which announced it has recalled pistachios in 31 states. Kroger operates stores under different names, including Kroger, Ralphs and Dillons.
For that reason, it could take weeks or longer to determine where all the pistachios ended up. They are used as ingredients in baked goods, and in trail mix and ice cream. So for now, the FDA has urged consumers to forgo this kind of nut entirely.
That is of obvious concern to California's Western Pistachio Association.
"We just hope the FDA comes out very quickly with a more refined statement about which pistachios to avoid, because the vast majority of the pistachios are not tainted," the association's executive director Richard Matoian told ABC station KFSN in Fresno, Calif.
"This is really the first day of what may be a very large recall when you consider all the products that could potentially contain these contaminated pistachios," DeWaal said.
Pistachio Recall Unrelated to Peanut Recall
The pistachio announcement came on the same day that the new acting commissioner of the FDA started his job. In taking the reins of the agency, Josh Sharfstein faced food safety challenges coming at him from several different directions.
For months, consumers have been warned to stay away from certain types of peanuts and shop for alternatives as salmonella spreads across the country.
As a result of those problems, peanut sales have plummeted, and lawmakers have stepped in to examine why companies didn't catch the problem before it became an outbreak. The peanut company at the heart of the recall has since filed for bankruptcy.
Peanut recalls continue to pour in eight months after illnesses first surfaced.
"The raw material providers need to tighten up their procedures, watch for cross contamination and be vigilant with pest control," said Jerry Kelly, a senior technical consultant with Specialized Technology Resources, a group that does quality assurance work that includes food testing.
"Everyone knows what they should do, they just need to tighten it up and document it a little better," Kelly told ABC News.
FDA officials also said all pistachio products were from the same 2008 crop year.
"The fact that a customer of the company found the problem is a sign that at least somebody's watching," DeWaal said. "But consumers certainly wish that the government had a more robust system so they could identify these problems before they even leave the plant."
A full list of recalled products, including Kraft Back to Nature Nantucket Blend Trail Mix and Kroger's Private Selection Shelled Pistachios, can be found on the FDA's Web site.
Symptoms of salmonella include fever, diarrhea, nausea, vomiting and stomach pain.
ABC News' Brian Hartman contributed to this report.