Another ten people have required hospital care, including a child who developed severe kidney complications. All stated that they had eaten at McDonald's a short time before falling ill, and most specifically mentioned the "Quarter pounder" hamburger. The cases of illness have occurred in several different states.
A preliminary investigation conducted by the US Food and Drug Administration (FDA) suggests that the sliced onions served on the hamburgers are a likely source of contamination, while the US Department of Agriculture is investigating the beef itself.
McDonald's claims that onions from a specific supplier may be the culprit. The restaurant chain has now paused the use of the onions and temporarily removed the "Quarter pounder" hamburger from the menu in several states.
"We take food safety extremely seriously, it's the right thing to do," McDonald's states in a statement.