While many Americans are concerned about Islamic State militants eventually infiltrating the United States, a former CIA operative claims that it’s already happened.

CNN national security analyst and former CIA operative Bob Baer said on “The Lead” Tuesday that the “people who collect tactical intelligence on the ground, day-to-day – and this isn’t Washington – but people collecting this stuff say they’re here, ISIS is here, they’re capable of striking.”

Credit: CNN's "The Lead"

CNN national security analyst and former CIA operative Bob Baer (Credit: CNN’s “The Lead”)

At this moment, he said, U.S. intelligence agents are keeping tabs on suspected Islamic State militants who may have crossed the Mexican border to gain entry into the United States. Other suspects, he warned, are American citizens who have returned from places like Syria.

“They can’t prove it. They’re waiting to get enough intelligence to actually run them in. And then there’s the unknown, of how many people have come back they’re not even aware of,” Baer told CNN. “The people who do this for a living are very alarmed.”

While intelligence officials aren’t entirely sure of the “plans or intentions” of possible Islamic State cells, they realize the threat alone is a “definite concern.”

Watch Baer’s interview on CNN:

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