The sole source of the U.S. salmonella outbreak involving contaminated peanut butter appears to be the Peanut Corp of America's Blakely, Georgia processing facility, federal officials said on Wednesday.

More than 125 products including cookies, crackers, ice cream and even some pet food have been recalled in connection with the outbreak, the U.S. Food and Drug Administration said.

Six deaths may be associated with the outbreak, the U.S. Centers for Disease Control and Prevention said. The CDC said at least 486 people from 43 states and one person in Canada have been reported ill from the outbreak of the Salmonella typhimurium strain, with 107 of them being hospitalized.

Stephen Sundlof, director of the FDA's Center for Food Safety and Applied Nutrition, said Connecticut health authorities tested an unopened container of peanut butter from the PCA's Blakely plant and discovered the strain linked to the outbreak of illness.

The fact that the unopened container had the strain indicates contamination did not occur after it was shipped from the facility, Sundlof said. Coupled with previous evidence, Sundlof said authorities believe the Blakely plant is the only source of the outbreak.

"That is our assumption at this point. We will continue to follow up on any leads that point us in a different direction," Sundlof told reporters during a conference call.

The plant is not currently operating, he said.

Sundlof said he expects the number of recalled products to continue to increase.

Among the latest was by NutriSystem Inc, which announced on Wednesday a voluntary recall of its peanut butter granola bar. On Tuesday, PetSmart Inc, the largest U.S. pet-products and services retailer, recalled seven of its Grreat Choice Dog Biscuit products.

General Mills Inc, Kellogg Co and other companies also have recalled products.

Authorities say peanut butter sold on grocery store shelves does not appear to be involved.

PCA has recalled peanut butter and peanut paste products manufactured since July at the Blakely plant because of potential Salmonella contamination. Peanut paste is a concentrated product consisting of ground, roasted peanuts.

PCA manufactures peanut butter and peanut paste distributed to food manufacturers to be used as ingredients in commercially produced products. PCA peanut butter also is served in long-term care facilities and cafeterias.

Salmonella can cause abdominal cramping, diarrhea and fever and it can kill the very young and very old.

"More cases are being reported every day. The outbreak appears to be ongoing," Dr. Robert Tauxe of the CDC said.

Minnesota authorities previously tested an opened container from the plant, and found the Typhimurium strain.

Sundlof said a federal inspection of the Blakely plant turned up evidence of salmonella on the floor, but not the Typhimurium strain.

"It does indicate that there are problems within the plant because salmonella should not be found there," he said.