Dozens of suspected radicals in the United States are under “tight surveillance” because law enforcement officials fear they might try to pull off a copycat version of the Paris attacks after being exposed to ISIS propaganda, according to FBI Director James Comey, during a rare joint briefing with U.S. Attorney General Loretta Lynch on Thursday.

The news came as senior law enforcement officials told ABC News Thursday that they are aware of a possible second ISIS video threatening Washington, DC. Authorities believe the video is part of an ISIS propaganda campaign to scare the American public in the wake of the Paris attacks. However, officials maintain that they have not identified a specific, credible plot targeting the U.S. homeland.

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