Three steroids were previously marked as dietary supplements but sold on the shelves of nutrition stores were recently classified as controlled substances by the Drug Enforcement Administration.

Madol and two other drugs, boldione and 19-nor-4,9(10)-Androstadienedione, were the drugs classified as steroids.

Travis Tygart, the head of the United States Anti-Doping Agency, said his agency has discovered at least 20 other steroids marked as supplements that are still not classified as controlled substances.

From NYTimes.com:

Under a rule that will take effect Jan. 4, the D.E.A. has classified a substance known as Madol and two other drugs — boldione and 19-nor-4,9(10)-Androstadienedione — as anabolic steroids, meaning it is now a crime for retailers to sell supplements that contain these substances. As controlled substances, some anabolic steroids can be used legally, if a doctor writes a prescription for a patient to treat a legitimate medical condition.

In a telephone interview, Tygart said that antidoping officials have known about and tested for all three substances for years. Madol was first identified six years ago during the investigation into the Bay Area Laboratory Co-operative. Earlier this year, Madol was the focus of an F.D.A. inquiry into a manufacturer, American Cellular Labs, that authorities said was marketing the drug as a legal alternative to steroids.

In 2008, the D.E.A. identified 58 products containing the three steroids that are the subject of its most recent rule. Tygart said he purchased a supplement containing Madol one week ago.

Under the Anabolic Steroid Control Act of 2004, scientists need to confirm that the chemical structure of a drug is like testosterone to term it as an anabolic steroid. After this, a laboratory has to prove that it can synthesize the specific drug in a controlled environment.