McDonald's Quarter Pounders will return to the menu at locations where sales of the hamburgers had been paused amid an E. coli outbreak, after beef was ruled out as the source.

The E. coli infections, first reported on Sept. 27 in Colorado, were linked to the recent consumption of Quarter Pounder hamburgers. The Food and Drug Administration, one of several authorities investigating the outbreak, has said that the slivered onions on the burgers are a "likely source of contamination."