An outbreak of salmonella in Illinois and four other Midwestern states was likely caused by pre-cut melon, federal health officials said Friday. Six people in Illinois have been sickened by the outbreak.

The U.S. Food and Drug Administration is investigating 60 infections across five states — Illinois, Indiana, Michigan, Missouri and Ohio. So far, there have been 31 people hospitalized; no deaths have been reported.

Most people reporting illness said they bought pre-cut melon from Walmart or Kroger stores. The chains removed the products linked to the outbreak from the shelves on Thursday, according to the Centers for Disease Control and Prevention.

Residents of Illinois, Indiana, Michigan, Missouri and Ohio, are advised to throw away all pre-cut melon bought from Walmart, Kroger, Jay C or Payless stores, including fruit salad mixes. Whole melons are not affected, the CDC said.