The AP just reported that California based Natural Selection Foods may be the missing link in this ongoing outbreak:

Natural Selection Foods LLC said in a statement that it was cooperating with federal and state health officials to identify the source of the contamination and had stopped shipping all fresh spinach products. They are sold under the brand names Rave Spinach, Natural Selection Foods, Dole, Earthbound Farm, Trader Joe’s, Ready Pac and Green Harvest.

More to come in the morning I am sure.