While the cause of the outbreak of salmonella typhimurium, which infected 399 people in 42 states, has not officially been determined, Minnesota agriculture and health officials Friday issued a product advisory for King Nut creamy peanut butter after preliminary testing, USA Today reported.

The investigators found the presence of salmonella in a 5-pound container of the sandwich spread, which is mostly used in schools, hospitals, long-term care facilities and restaurants, the newspaper said.

"We pulled the sample peanut butter from one of the nursing homes that had ill patients connected to this outbreak," Doug Schultz of the state's health department told USA Today.

The outbreak began in mid-October and affected 55 people in California, 53 in Ohio, 39 in Massachusetts, 30 in Minnesota and 20 in Michigan 20, the U.S. Centers for Disease Control said.