Six executives with USPlabs LLC and a related company, S.K. Laboratories, face criminal charges related to the sale of unlawful dietary supplements. Four were arrested on Tuesday and two are expected to surrender, the Justice department said.

The indictment says that USPlabs used a synthetic stimulant manufactured in China to make Jack3d and OxyElite Pro but told retailers that the supplements were made from plant extracts.

"The defendants knew of studies that linked the products to liver toxicity," the department said in a press statement.

News of the impending press conference earlier sent share prices of GNC Holdings Inc (>> GNC Corporation), Vitamin Shoppe (>> Vitamin Shoppe Inc) and Herbalife Ltd (>> Herbalife Ltd.) lower. But those companies were not named in the subsequent announcement and all recovered to close down slightly.

GNC Holdings closed down 6.4 percent, Vitamin Shoppe ended down 5 percent and Herbalife slipped 1.5 percent.

Along with the Justice Department, the news conference was attended by representatives of the U.S. Food and Drug Administration, the U.S. Postal Inspection Service, the Federal Trade Commission, the Department of Defense and the U.S. Anti-Doping Agency.

(Reporting by Siddharth Cavale in Bengaluru and Diane Bartz in Washington; Editing by Bernard Orr)