A committee of the congressionally chartered group was set to release the report on Tuesday.
The FBI sought the independent review amid skepticism in some quarters about its findings that the late Army researcher Bruce Ivins acted alone in making and sending the deadly powder.
Investigators have acknowledged that their case against Ivins is circumstantial. They used new and emerging science to conclude the parent material of the anthrax spores used in the mailings came from a single flask in Ivins' laboratory at Fort Detrick in Maryland.
