Though no credible or specific threats have been identified, the FBI and Department of Homeland Security have released a bulletin to 18,000 law enforcement agencies across the country warning of copycat attacks, similar to the Paris terrorist strikes that killed 130 people earlier this month.

According to ABC's "World News Tonight with David Muir," the bulletin notes that, "Homegrown radicals inspired or directed by Syria-based operatives, could seek to replicate the effects of the Paris attacks using similar weapons and tactics, although on a smaller scale."

They also warn the police "to be on the lookout for suspicious people conducting surveillance on soft targets in the United States," NBC News reports.

With an expected 47 million people traveling for Thanksgiving, Polly Hanson, the Chief of the Amtrak Police Department, showed ABC correspondent Pierre Thomas the precautionary measures they are taking including deploying officers stationed with long guns, explosive detection canines, and special agents with tactical skills.

Law enforcement agencies say there is no evidence that ISIS individuals will travel from Syria to the U.S. to plan attacks as they did in Paris, but the FBI is honing in on the ISIS followers that are potentially already on U.S. soil.