The investigation into the E. coli outbreak in McDonald’s Quarter Pounders that has killed at least one person and sickened nearly 50 others increasingly points to the slivered onions served on the hamburgers.
But neither the company nor public health officials have said publicly where the onions were grown or whether they were sent to other restaurants, as well.
The onions in question, according to a McDonald’s spokesperson, come from a single source and are then sliced and packaged as raw vegetables in individual bags and sent to restaurants.
“It’s a raw onion process at a facility and then sent to McDonald’s,” the spokesperson said.
McDonald’s has pulled the sliced onions and quarter-pound beef patties, both used for the Quarter Pounder burgers, from its menu in affected areas.
The strain of E. coli in the outbreak, called O157:H7, produces a powerful toxin that can damage the lining of the small intestine, according to the Mayo Clinic.