ATLANTA — A federal probe into a deadly salmonella outbreak has exposed a dirty secret: Food producers in most states are not required to alert health regulators if internal tests show possible contamination at their plants.

The legal loophole surfaced this week when federal investigators disclosed internal Peanut Corp. of America reports that documented at least 12 positive tests for salmonella between 2007 and 2008 at their Blakely, Ga., plant, which has been identified as the source of the nationwide outbreak. In each case, the plant did not alert state or federal regulators.

The flaw has infuriated regulators and food safety experts, who are pushing legislation that would require the alerts at the first sign of contamination. They say stricter requirements could have stemmed an outbreak, which may have started months ago and has sickened at 529 people and may have led to eight deaths.

"Nobody was looking over their shoulder," said Caroline Smith DeWaal, director of food safety for the Center for Science in the Public Interest. "And if they knew state officials could have viewed that data, they might have made different decisions. And that could have saved lives."

Peanut Corp. tests showed salmonella had been found in products made at the plant in southwest Georgia dating to 2007. Still, production lines were never cleaned, according to a Food and Drug Administration report. The products that initially tested positive were retested and shipped after a different test by a different firm came up negative.

Federal officials, food scientists, legal experts and industry groups, including the Grocery Manufacturers Association, cannot point to a state that requires food producers to alert health regulators about positive contamination tests. That includes three of the biggest agricultural states — California, Texas and Florida.

While there is nothing that requires companies to disclose to either the public or regulators internal test results, the Food and Drug Administration does have the authority under the Bioterrorism Act of 2002 to obtain the records when it considers it valuable to investigating an outbreak, said agency spokeswoman Stephanie Kwisnek.

The FDA has only exercised that authority three times, including this latest outbreak. It was after it received Peanut Corp.'s records that the FDA discovered that 12 internal tests had pinpointed batches of peanut butter containing the salmonella bacteria.

The agency also used the Act in the 2007 melamine investigation that led to a massive recall of pet food. Unscrupulous suppliers in China had been adding the industrial chemical to pet food ingredients to artificially boost protein readings on quality tests. It caused kidney problems, even death.

Federal lawmakers are pushing for vast changes to food safety inspection policy. Rep. Bart Stupak, D-Mich., who heads a congressional panel looking into the outbreak, and Rep. Henry Waxman, who chairs the House Energy and Commerce Committee, said they will hold a hearing next month on the problem.

"The situation at the plant is alarming," said Waxman, D-Calif. "It shows major gaps in our food safety system. I am extremely troubled by reports that the plant tested positive for salmonella numerous times but nothing was done to ensure that the product did not go on the market."

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Some states do have laws that give regulators more tools to access internal reports. California, an agricultural powerhouse, allows access to internal records if regulators request them as part of a survey or an inspection. But it doesn't require the plants to submit them on their own.

But Fred Pritzker, a food safety lawyer in Minneapolis, said he doubts any states have the requirement because those requirements would be more restrictive than the federal government.

Food makers not being required to share tests that show harmful bacteria has long aggravated food safety experts and state regulators, who say these latest sicknesses are why the information is needed.

"It's obvious in this case that the company was finding salmonella in the plant, and that is a violation of good manufacturing practices. None of that product should have come out," said Tony Corbo of Food & Water Watch, a Washington-based advocacy group.

Peanut butter has long been considered a relatively low risk for salmonella because roasting the peanuts properly kills the bacteria, and because its low moisture content makes it a less fertile breeding ground. But during an inspection of the Blakely plant in January, federal inspectors reported finding roaches, mold, a leaking roof and other sanitary problems.

The company says it is cooperating with the government and has shut down production at the plant. Peanut Corp. said in a statement it "categorically denies any allegations that the company sought favorable results from any lab in order to ship its products."

Major peanut manufacturers, including Jif maker J.M. Smucker Co., Skippy manufacturer Unilever and ConAgra Foods Inc., which makes Peter Pan, have said they have stringent food safety and quality control standards. But they wouldn't say how often their plants test the finished product. None is implicated in the outbreak.

Federal lawmakers and Georgia politicians are calling for a federal probe of possible criminal violations at the plant.

And Georgia Agriculture Commissioner Tommy Irvin said he wants his state — the nation's leading peanut producer — to be the first to require plants to alert regulators about positive contamination tests.

"If they deem it necessary to do some in-house testing, then we want access to it," Irvin said.

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