(CNN) — Wolverine Packing Co. is recalling more than 167,000 pounds of ground beef shipped to restaurants due to possible E. coli contamination. So far, 15 patients have been reported ill in Minnesota, with illnesses starting from November 2 to November 10, the US Department of Agriculture Food Safety Inspection Service said Wednesday. Fresh products have a use by date of Nov. 14. Frozen products are labeled with production date of Oct. 22. Products have an establishment number EST. 2574B in the USDA mark of inspection. Items were shipped to restaurants nationwide, the FSIS said, and it’s concerned that some products may be in restaurant refrigerators or freezers. All the products should be thrown away or returned and should not be eaten. The Minnesota Department of Agriculture notified FSIS on November 13 about illnesses in people who had eaten ground beef. On November 20, a ground beef sample collected by the Minnesota Department of Agriculture tested positive for E. coli O157. People with E. coli infections may have symptoms including severe stomach cramps, diarrhea, fever and vomiting. Symptoms of infection usually begin three or four days after swallowing the bacteria. Although most people who become ill recover without treatment within a week, others can develop serious kidney problems and require hospitalization.