Food and Drug Administration

Romaine lettuce made 172 people sick. The FDA may never know why.

Romaine lettuce made 172 people sick. The FDA may never know why.

More than seven weeks after the start of a massive E. coli illness outbreak from romaine lettuce that sickened 172 people and caused romaine sales to plummet 45 percent, the Food and Drug Administration says it has no idea who or what caused the contamination.

Agency investigators have not managed to trace the affected lettuce back to one farm, processor or distributor, FDA Commissioner Scott Gottlieb said in an update Thursday. And with the affected lettuce now off shelves and the growing season over, there's a chance the FDA may never crack the case.

The mystery has frustrated consumer advocates, who have called on the FDA to issue rules that would speed up future...

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