Popular fast-food restaurants are holding the onions after the vegetable was identified as the likely source of the E. coli outbreak among Quarter Pounder hamburgers at McDonald's. Some of those who got sick after eating the Quarter Pounder are also going after the Chicago-based company in court.

The top U.S. McDonald's executive said he’s “very confident” customers can eat safely at the restaurants, as the company's stock heads to its worst day in 4.5 years

The McDonald's Quarter Pounder is part of a "classics" menu that drives huge sales. The giant says it's temporarily pulling the item from menus.