"It would seem to me to be improbable that a domestic extremist would be able to put together such an attack in such a short period of time," he said.
Twenty-two of them were classified as domestic extremist or separatist cases, and a further four were "historic cases", dating back to the 1980s and 1990s.
Some senior officials suspect the anthrax letters are the work of domestic extremists fueled by anti-government hatred.
They see cyberterrorists everywhere - foreign nations, international criminal gangs and domestic extremists.
But unless moderates take a stand against the growing power of domestic extremists, it can happen here.
In an age of constant electronic communication and incessant analysis, it would be difficult and painful to acknowledge that in the end there was no sure defense against either international or domestic extremists.
Are you a 'domestic extremist'?
But recent history has shown that terrorism against Americans can just as easily come from domestic extremists.
In the Annual Report details of the activities of far right, far left, Islamic extremists foreign and domestic, in Germany, as well as espionage, are given.