The investigative arm of Congress will conduct its own review of the Federal Bureau of Investigation’s scientific work in concluding that Bruce E. Ivins, an Army scientist, mailed the anthrax letters that killed five people in 2001. Colleagues of Dr. Ivins, who killed himself in 2008, have questioned the bureau’s finding. The review, to be conducted by the Government Accountability Office, will begin after an anthrax study by the National Academy of Sciences is completed this year. At the F.B.I.’s request, an academy panel has been looking at the genetic and chemical analysis of the powder and other work on the case by the F.B.I. and its consultants. Representative Rush Holt, Democrat of New Jersey, who has long sought an independent review of the work, praised the G.A.O.’s decision.