(CNN) - Consumer Reports found listeria in leafy greens from a variety of grocery store chains, according to a new report.
Consumer Reports purchased samples of leafy greens from Whole Foods, Costco, Hannaford, and Acme stores in Connecticut, New York, and New Jersey
Out of 284 samples, six were tainted with Listeria monocytogenes -- four in bunches or loose heads and two in pre-washed, 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.
Health experts say the people most likely to be impacted by listeria are young children, the elderly, pregnant women, and those with compromised immune systems.
They say you can still eat leafy greens, just stick with the cooked varieties.
Consumer Reports says it decided to test leafy greens for bacteria after several outbreaks linked to romaine lettuce. While they did find listeria, they did not find any other bacteria that cause foodborne illness such as salmonella and E. coli.
While they say few people likely still have any of the products in their homes, those who bought products from those stores in early to mid-June should wash or sanitize their crispers or wherever the greens were stored.