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

The Quarter Pounder is back on the menu after testing showed no signs of E. coli. But the popular burger won’t feature the slivered onions, as they’re the likely source of the outbreak in multiple states that sickened at least 75 people, McDonald’s said Sunday.

McDonald's will resume selling Quarter Pounder hamburgers in all restaurants this week, as it was informed results of testing showed no detection of E.coli in the beef patties, the U.S. fast-food giant said.