The organization purchased samples of leafy greens from Whole Foods, Costco, Hannaford, and Acme stores.
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Out of 284 samples, six were tainted with listeria monocytogenes -- four in bunches or loose heads and two in prewashed, prepackaged salad mixes.
Consumer Reports points out that its sample size wasn't big enough to support any conclusions about the safety of specific stores or specific brands, adding that the results show more needs to be done to ensure the safety of leafy greens.
The findings prompted an FDA investigation, but no results have been released so far.
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