WASHINGTON (March 1) - 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.

"The fact that FDA found salmonella in the plant environment further suggests that the contamination likely took place prior to the product reaching consumers," the agency said in a statement.

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. Health officials warned the public to discard the products, some of which have been recalled.

The products are:

Sonic Brand Ready-To-Use Peanut Butter Topping in 6 lb. 10.5 oz cans. Sonic outlets used the topping until Feb. 16, when the product was recalled.

Carvel Peanut Butter Topping in 6 lb. 10 oz. cans. Carvel also used the topping until Feb. 16, when it too was recalled.

J. Hungerford Smith Peanut Butter Dessert Topping in 6 lb. 10 oz. cans. The topping is used by retail outlets and restaurants nationwide but is not available for direct purchase by the public, the FDA said.

Government and industry officials have said the contamination may have been caused by dirty jars or equipment. Peanuts are usually heated to high, germ-killing temperatures during the manufacturing process. The only known salmonella outbreak in peanut butter - in Australia during the mid-1990s - was blamed on unsanitary plant conditions.