Minnesota state health officials are investigating seven cases of E. coli infection in Minnesotans who ate ground beef purchased at Lunds or Byerly’s grocery stores.  Routine monitoring by the Health Department found the illnesses were all caused by E. coli O157:H7 bacteria with the same DNA fingerprint. All involved ground beef purchased from one of four Lunds or Byerly’s stores in the western Twin Cities metro area since April 12.  The Byerly’s stores are in St. Louis Park, Minnetonka and Chanhassen, and the Lunds is in Edina.  Five adults and two children became ill between April 21 and 28. Three were hospitalized, but all have since been discharged.