Grady Jackson, a defensive tackle with the Atlanta Falcons, said he used the weight-loss capsules. Kathie Lee Gifford was enthusiastic about them on the “Today” show. Retailers like GNC and the Vitamin Shoppe sold them, no prescription required.

But the Food and Drug Administration now says those weight-loss capsules, called StarCaps and promoted as natural dietary supplements using papaya, could be hazardous to your health. In violation of the law, the agency has found, the capsules also contained a potent pharmaceutical drug called bumetanide which can have serious side effects.

And StarCaps are not the only culprits. In a continuing investigation that has prompted consumer warnings and recalls by some distributors, the F.D.A. has determined that dozens of weight-loss supplements, most of them imported from China, contain hidden and potentially harmful drugs. In the coming weeks, the agency plans to issue a longer list of brands to avoid that are spiked with drugs, an F.D.A. spokeswoman said.

Besides StarCaps, which were made in Peru and which Balanced Health Products, the American distributor, has voluntarily withdrawn, the agency’s warning list includes more obscure pills sold under the names Sliminate, Superslim and Slim Up, among many others. So far, the F.D.A. has cited 69 tainted weight-loss supplements.