While the bacteria in the peanut butter match the outbreak strain genetically, the health officials said it was not clear yet that the peanut butter could be linked to any cases.

The outbreak of salmonella food poisoning has sickened at least 399 people and put 70 or more into hospital since September.

Officials from Minnesota's departments of agriculture and health said they were issuing a product advisory for King Nut brand creamy peanut butter after finding the Salmonella typhimurium bacteria in a big institutional-size jar.

"The Minnesota cases have the same genetic fingerprint as the cases in a national outbreak that has sickened almost 400 people in 42 states," the health department said in a statement.

It said the product was distributed in Minnesota to places such as long-term care facilities, hospitals, schools, universities, restaurants, cafeterias and bakeries.

"At this time, the product is not known to be distributed for retail sale in grocery stores," it said. "State officials are urging establishments who may have the product on hand to avoid serving it, pending further instructions as the investigation progresses."

Earlier on Friday, the U.S. Centers for Disease Control and Prevention listed the numbers of cases in each of the 42 affected states. California was hardest hit with 55 cases, while Ohio had 53 and Minnesota had 30.

An outbreak of salmonella was linked to Peter Pan brand peanut butter in 2007. ConAgra Foods Inc closed a Georgia plant after more than 300 people became ill in that outbreak.

The CDC is trying to trace the source of the outbreak, which began in September. The U.S. Department of Agriculture, state health officials and the Food and Drug Administration are also involved.

Tracking the source of such an outbreak can be tricky. The CDC said poultry, cheese and eggs are the most common source of Salmonella typhimurium strains.

Every year, about 40,000 people are reported ill with salmonella in the United States, the CDC says, but many more cases are never reported.

There have been several high-profile outbreaks of foodborne illness in the United States, including a strain of salmonella carried by peppers from Mexico that sickened 1,400 people from April to August 2007 and an E. coli epidemic in 2006, traced to California spinach, that killed three people.

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