Four major supplement retailers—GNC, Target, Walmart, and Walgreens—have been accused of selling store-brand herbal supplements in New York that were either entirely void of the labeled substance or found to contain unlabeled ingredients, according to a press release from New York Attorney General Eric T. Schneiderman. The findings come from DNA testing of 7 herbal supplements—echinacea, ginseng, St. John’s Wort, ginko biloba, garlic, valerian root and saw palmetto—performed by the Attorney General’s Office. The investigation was sparked by a 2013 University of Guelph study, which found that most herbal supplements contained additives or substitutions that weren’t listed on the label. Overall, only 21% of products tested contained the plant material listed on the products’ labels. The other 79% either had none of the actual plant material advertised, or were contaminated with “fillers” or unidentified ingredients, including powdered rice and houseplant(!). The retailer with the poorest track record was Walmart, with only 4% of their products confirmed as containing the herbs listed on the product labels. MORE: Are Your Herbal Supplements Safe? Since the announcement, all four stores have removed the products in question from their shelves—Walgreens and Target nationwide; Walmart and GNC in New York. Schneiderman indicates that these four offenders are likely just a fraction of the problem. “This investigation makes one thing abundantly clear: The old adage ‘buyer beware’ may be especially true for consumers of herbal supplements,” he said. And there are a lot of those consumers: According to the National Products Foundation, the dietary supplement industry contributes $61 billion to the national economy, while a 2013 Canadian Institutes of Health Research study found that the 65,000 dietary supplements on the market are taken by more than 150 million Americans. Further, more than half of the Food and Drug Administration (FDA) Class I recalls between 2004 and 2012 were—you guessed it—dietary supplements. (Those Class I recalls indicated a “reasonable probability” that the supplements would cause serious, adverse health consequences or death.) Despite all the fuss, Prevention editors have reason to suspect that all is not what it seems. Last year we reported on a supplement study using the same type of DNA testing that turned out to be widely discredited. Stay tuned for more information. MORE: 21 Healing Herbs And Supplements Doctors Prescribe