The U.S. Food and Drug Administration continues to believe that slivered onions from a single supplier are the likely source of contamination.

The Colorado Department of Agriculture's testing did not detect E. coli in samples of the beef patties taken from McDonald's restaurants in the area.

All contaminated products related to the E. coli outbreak that sickened 75 people across 13 states, with one reported fatality, are now fully out of McDonald's restaurants, the company said in a statement Sunday.