ALBANY, N.Y. >> Fourteen attorneys general asked Congress to launch an investigation of the herbal supplements industry and to consider giving the U.S. Food and Drug Administration stronger oversight of the industry, New York Attorney General Eric Schneiderman announced.

"When consumers take an herbal supplement, they should be able to do so with full knowledge of what is in that product and confidence that every precaution was taken to ensure its authenticity and purity," Schneiderman said Thursday.

Schneiderman alleged in February that DNA tests on certain store-brand supplements found none of the herbs on the labels. Industry groups and some consumer advocates have criticized Schneiderman’s test method, saying DNA testing is unable to identify highly processed plant material.

GNC, one of the retailers targeted by Schneiderman, said last week that it has provided him test results from independent labs showing its products were safe and properly labeled, and has agreed to add DNA testing to its quality control procedures.

Daniel Fabricant, former director of the FDA’s dietary supplement division and now executive director of the Natural Products Association trade group, called the attorney generals’ action "harassment based on science fiction."

"For the past two months, the attorney general has continued to escalate his attack on the supplement industry without any legitimate data to back up his arguments," Fabricant said.

Under federal law, herbal supplements, vitamins and other dietary supplements are subject to far less rigorous oversight than pharmaceutical products.

There is no regulation that requires a firm to disclose to the FDA or consumers the information it has about the safety or purported benefits of dietary supplements, according to agency’s website. The manufacturer is responsible for ensuring the ingredient list is accurate. The FDA can take action against supplements only after they are proven to be unsafe.

Schneiderman noted research has found some herbal supplements to contain high levels of heavy metals like lead, mercury, and arsenic, and pointed to a study that found a popular herbal supplement designed to reduce menopause symptoms may have caused severe liver damage in certain women.

"The FDA has long been aware of problems in the dietary and herbal supplement supply chain, from dubious ingredient sourcing to a failure to carry out proper testing on finished products," the attorneys general said in their letter sent Thursday to Kansas Sen. Jerry Moran and Pennsylvania Rep. Joe Pitts, chairmen of the subcommittees dealing with product safety and health.

Steve Mister, president of the Council for Responsible Nutrition, an industry group, said concerns raised in the letter about widespread safety issues are untrue.

"Our association will certainly cooperate and answer any questions Congress may have about our industry as we share the common goal of making sure that consumers have access to the safe and beneficial herbal supplement products they use to improve their health and well-being," Mister said.

Schneiderman’s letter is co-signed by the attorneys general of Connecticut, District of Columbia, Hawaii, Idaho, Indiana, Iowa, Kentucky, Massachusetts, Mississippi, New Hampshire, Northern Mariana Islands, Pennsylvania and Rhode Island.