Washington, D.C. ? Federal inspectors found the strain of salmonella behind a recent food-poisoning outbreak at the ConAgra Foods Inc. plant that made the tainted peanut butter, the Food and Drug Administration said Thursday.

Beyond the Sylvester, Ga., plant, the strain also has been isolated from open jars of the company’s peanut butter and some of the 370 people who have fallen ill in the outbreak, the FDA said.

ConAgra on Feb. 14 recalled all Peter Pan and Great Value peanut butter made at the Georgia plant after federal health officials linked the product to an outbreak that began in August. The recall now includes all such products made since December 2005, the FDA said.

On Thursday, the FDA said the company had sent bulk Peter Pan peanut butter to its plant in Humboldt, Tenn. There, it was incorporated into various ice cream, sundae and shake toppings – used primarily by retail outlets – that also have been recalled.