The Georgia peanut processing plant at the center of a national salmonella outbreak had a history of problems it failed to correct, federal health officials said Tuesday.

Officials said the Peanut Corp. of America plant had shipped products that the company's own initial tests found to be positive for salmonella. They retested and got a negative reading.

Peanut Corp. also failed to take some standard "good manufacturing" steps to prevent contamination within the Blakely, Ga., facility. officials said. Indeed, investigators have identified four different strains of salmonella thus far.

"There is certainly a salmonella problem in the plant," said Dr. Robert Tauxe of the Centers for Disease Control and Prevention.

The latest findings renewed concerns about federal inspections of food facilities, which are few and far between. In this case, the Food and Drug Administration relied on Georgia authorities to inspect the plant. But state agricultural inspectors did not uncover what now appears to have been a festering problem.

"Inspections are worthless if companies can test and retest until they receive the results they want," said Rep. Bart Stupak, D-Mich, who heads a congressional panel conducting its own inquiry. He's introduced legislation to end such "lab shopping" and to require companies to submit all test results to the FDA. Officials said Peanut Corp. did not initially disclose the test results that found salmonella.

Meanwhile, the recall list has grown to more 390 products, from ice cream to dog biscuits. More than 500 people have gotten sick, and the outbreak may have contributed to eight deaths.

Peanut Corp. issued a terse statement on Tuesday, saying: "PCA has cooperated fully with the FDA from day one during the course of this investigation. We have shared with them every record that they have asked for that is in our possession, and we will continue to do so."

The FDA said it will post its inspection reports on the Internet on Wednesday.

A senior FDA investigator told reporters Tuesday that the company's own internal testing detected salmonella on about 12 occasions in 2007 and 2008.

"The inspection revealed that the firm's internal testing program identified salmonella," said Michael Rogers, director of FDA's division of field investigations. "In some cases ... a subsequent lab was used that reached a negative conclusion." Peanut Corp. then shipped the products.

But, said Rogers: "At the point in which salmonella was identified, it shouldn't be there."

Rogers also said Peanut Corp. did not do enough to prevent cross-contamination within the plant. Roasting is supposed to kill any salmonella in peanuts. But roasted peanuts can become re-contaminated if they are handled with equipment that's also used for raw peanuts.

Health officials said they have now identified four types of salmonella in connection with the investigation.

Salmonella Typhimurium is the strain that caused the illnesses. Two other strains were found on the floor of the facility and a third in a container of peanut butter from the plant.

Stupak, whose staff has been briefed by the FDA, said Salmonella Tennessee was found in an unopened jar of peanut butter from the plant.

Salmonella Senftenberg, as well as Salmonella Mbandaka were found on the floors of the plant.

None of the other three strains contributed to the outbreak, CDC officials said, but their presence was seen a sign of overall problems with cleanliness at the facility.

Curiously, the outbreak strain has not turned up within the plant. Nonetheless, officials said they have plenty of evidence that's where it came from. Connecticut health officials isolated Salmonella Typhimurium from an unopened container of peanut butter made at the facility. Minnesota officials found it in an open container. FDA also found it in a package of recalled crackers made with peanut paste from the plant.

Salmonella is the most common source of food poisoning in the United States. It causes diarrhea, cramping and fever. About one out of every five patients who got sick in the current outbreak had to be hospitalized. The elderly and the very young are especially vulnerable.

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On the Net:
FDA's outbreak page: http://tinyurl.com/8srctw