Unlike drug makers, which must demonstrate that a drug is safe and effective before the agency approves it for sale to the public, dietary supplements are a largely self-regulating industry. Manufacturers of such products are themselves responsible for the safety and effectiveness and marketing claims of their products, and for voluntarily recalling them if problems arise. The F.D.A. has authority to act only after it has received reports of serious health problems associated with products already on sale and it is able to prove a serious health hazard. If a company refuses to voluntarily recall problem products, the agency can then file an injunction and seize the products.

Image Tren Xtreme and Mass Xtreme are among the eight supplements cited by the F.D.A. as containing steroidlike substances.

Such a reactive strategy puts consumers at risk, critics said.

“I applaud what the F.D.A. is doing, but the law handcuffs their hands behind their backs when they are dealing with the tsunami of products that get on the shelves,” said Mr. Tygart, the antidoping official. “This shows a glaring light on the ineffective regulatory scheme that allows these products to get to the market.”

He added: “The reality is that these products are still out, and consumers who don’t hear or read about the warning will continue to use them because it’s so hard to recall them.”

Over the last two years, the F.D.A. has received 15 reports of serious health problems  including stroke, liver problems and pulmonary embolism  associated with body-building products from various makers, the agency said. One of the five reports connected to American Cellular products concerned a 38-year-old man who had severe liver and kidney problems that needed to be treated with dialysis after he used the company’s products, according to warrants issued in the case.

Steroids are organic compounds, like hormones or cholesterol, that naturally occur in the body. Some compounds called anabolic androgenic steroids, which affect both the metabolism and the endocrine system, are approved as drugs to treat medical problems like testosterone deficiencies.

But the F.D.A.’s action pertains to unapproved forms of synthetic steroids  popularly known as designer steroids because they are intended to evade detection by sports authorities who test athletes for performance-enhancing drugs.