House Intelligence Committee Chair 'Not Sure' U.S. Can Track Americans Headed for Syria David Nunes concerned that people who have helped ISIS are returning to U.S.

 -- Devin Nunes, the chair of the House Intelligence Committee, said he is not sure that the U.S. will be able to track all of the Americans who have gone to Syria to help ISIS.

"This has long been a concern about fighters that go into Iraq and get back either into Europe or the United States," Nunes told ABC News' Martha Raddatz on "This Week."

The New York Times reported today that the number of Americans going to join ISIS in Syria has risen to over 250, an increase from approximately 100 a year ago.

But Nunes, R-California, said he is not confident the U.S. will be able to track all 250, despite the fact that the FBI has opened an investigation in all 50 states to find these Americans. He is also concerned that those who have left can return to the United States.

"I believe they're getting back into Europe," he said.

Over the past year, the Department of Justice has arrested multiple people on charges that they were conspiring to join ISIS or were planning ISIS-inspired attacks, including a National Guardsman and his cousin and the son of a respected Boston police officer.

Earlier this month, the Pentagon confirmed to ABC News that it is investigating allegations that Centcom’s intelligence on ISIS was distorted to provide a more positive picture.

Nunes, who also said he believed the White House’s current policy on fighting ISIS will not succeed, indicated that he believed those allegations to be true.

It has been "alarming," Nunes said, to look at the intelligence on the ground in Syria and compare it with the way the fight against ISIS is being portrayed by the White House.

"When you look at the final product and what the president has been saying, you look at the policies he's been implementing, it really makes me wonder, is it the analysts getting the information wrong or is it being politicized?" he said.