Although CAIR is a nonprofit organization, it does not disclose complete directories of its staff or advisory boards, and even refuses to make its federal tax filings readily available to the public.

But a review of federal criminal court documents, past IRS 990 tax records and Federal Election Commission records detailing donor occupations, reveals that Washington-based CAIR has been associated with a disturbing number of convicted terrorists or felons in terrorism probes, as well as suspected terrorists and active targets of terrorism investigations.

"Their offices have been a turnstile for terrorists and their supporters," said one FBI veteran familiar with recent and ongoing cases involving CAIR officials.