An ISIS member waves an ISIS flag in Raqqa.

Hundreds of Americans have traveled to Iraq and Syria to fight for ISIS and around 50 have returned to America, a senior U.S. lawmaker said Sunday.

That’s the kind of scenario that led to the Paris terror attacks of November 13, said Republican Congressman Michael McCaul, chairman of the House Homeland Security Committee.

“And the Paris attacks were the classic case of the foreign fighter,” McCaul told CNN, referring to a Syrian passport found near the body of one of the Paris attackers. The massacre left 130 dead and hundreds wounded.

“We’ve had hundreds of them travel over there and 50 have come back to the United States,” the congressman added.

More than 70 ISIS supporters were arrested in the United States last year and investigations are underway in all 50 states, he added.

McCaul said U.S. intelligence officials are also very concerned about the possibility of an insider job leading to a bomb being placed on a U.S.-bound airliner.

He said this is what happened with the Russian airliner that exploded over Egypt on October 31, killing all 224 people aboard. ISIS claimed responsibility.

“Someone was compromised or radicalized or perhaps bribed to put a piece of luggage, a bomb on the airplane. That is, a worker at the airport,” the congressman said.

That kind of threat is hard to stop, no matter how good a country’s screen technology is.

“That kind of scenario playing on an airliner flying directly into the United States is what I’m most concerned about,” McCaul added.

Another lawmaker, Republican Richard Burr, chairman of the Senate Intelligence Committee, said Sunday there is currently no credible, specific threat of a terror attack against the United States.

But over the past year, there have been more “threads of threats” in America and elsewhere in the world since the September 11, 2001 attacks in the United States.

“So the risk remains high,” Burr said.

He also said of ISIS that “to talk about containment is really a joke.”

“The reality is that ISIS may be geographically contained in Syria and Iraq, but their efforts around the world to project terrorism and to commit terrorism is as robust today as it’s ever been,” Burr said, using an alternative acronym for ISIS.

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