Rep. Michael McCaul (R-Texas) declined to go into detail about the determination, which the Obama administration has not announced publicly.

Yet the disclosure could add ammunition to critics of the White House’s refugee plans who have warned that the program is vulnerable to infiltration by adherents of the Islamic State in Iraq and Syria (ISIS).

“ISIS members in Syria have attempted to exploit it to get into the United States,” McCaul said during a speech at the National Defense University on Monday.

“The U.S. government has information to indicate that individuals tied to terrorist groups in Syria have already attempted to gain access to our country through the U. S. refugee program.”