But officials say "...some have disappeared and are suspected of having gone to al Qaeda training camps."
Read the Senate Committee Report
In addition, a smaller group of "...nearly 10 non-Yemeni Americans ... converted to Islam, became fundamentalists and married Yemeni women so they could remain in the country."
One official says these are the "blond-haired, blue-eyed types" al Qaeda seeks to recruit. But, the report says there is "no evidence that any of these Americans have undergone training."
Still, officials say "...they are on heightened alert because of the potential threat from extremists carrying American passports..."
The report also notes that officials fear American citizens are being recruited in Somalia for terrorist operations. It has been widely reported that a number of Americans have travelled there to train and fight with the terror group al Shabaab.
The report is being released in advance of a flurry of Capital Hill hearings tomorrow examining the failures that led to the attempted Christmas Day bombing by Umar Farouk Abdulmutallab. Abdulmutallab, a Nigerian travelling with a US visa, trained with al Qaeda in the Arabian Peninsula (AQAP).
CBS News producers Carter Yang and Laura Strickler contributed to this post.