In the latest attack on the natural products industry by state authorities, Oregon Attorney General Ellen Rosenblum on Thursday sued General Nutrition Corp. (GNC) for selling supplements that purportedly contain illegal ingredients.

Pennsylvania-based GNC has misrepresented that products containing BMPEA and picamilon are dietary supplements when they are actually unapproved drugs, according to the lawsuit. Researchers have described BMPEA as an amphetamine-like substance, while Rosenblum characterized picamilon as a synthetic chemical that has been used in some countries as a prescription drug to treat neurological conditions.

“It is scary to know that certain products sold by GNC contain an ingredient that is not even labeled—let alone approved in the United States," Rosenblum said in a statement.

GNC said the claims in the lawsuit lacked merit and the retailer intended to mount a vigorous defense. “In response to FDA statements regarding the regulatory status of BMPEA and picamilon, GNC promptly took action to remove from sale all products containing those ingredients," GNC said in a statement.

Rosenblum is at least the second state attorney general to target GNC in a supplement probe this year. In March, GNC reached an accord with New York Attorney General Eric Schneiderman to resolve an herbal supplement investigation in which Schneiderman claimed the retailer’s products failed to contain the labeled herbs.

The lawsuit against GNC reflects growing interest by attorneys general in cracking down on a dietary supplement industry that its critics maintain lacks adequate federal oversight and has a reputation for fraudulent behavior.

Earlier this year, Vitamin Shoppe announced reaching agreements with the Oregon and Vermont attorneys general to refrain from selling BMPEA-containing products. The agreements were reached just weeks after FDA demanded in warning letters that a handful of supplement companies cease distribution of products that contain BMPEA.

But FDA critics said the agency dragged its heels in taking action to remove BMPEA from the market. The agency has cited its limited resources and main focus on protecting public health.