U.S. federal counterterrorism authorities are tracking as potential threats a dozen or so ex-rebels trained in Syria who have returned to the United States.
In excess of 50 Americans have traveled to Syria to join the effort to topple President Bashar Assad's regime, according to officials. Some of these U.S. fighters may be part of al-Qaida-affiliated groups. Washington officials are concerned that the training they are receiving in Syria could be used to carry out attacks on the United States.
"We are concerned about the use of Syrian territory by the al-Qaida organization to recruit individuals ... to use Syria as a launching pad" for strikes on Western countries, CIA Director John Brennan told a House Intelligence Committee hearing on Tuesday.
Not all U.S. citizens fighting in Syria are Muslim or Syrian-American, the unidentified official sad.
"There is no single profile," the official said. "Some are going for humanitarian reasons and they get sucked into extremism."
The FBI has examined in excess of 12 individuals who traveled back to the United States, two anonymous U.S. officials said. Some in that group still are being monitored.
Testifying alongside Brennan, U.S. National Intelligence Director James Clapper said, "Not only are fighters being drawn to Syria, but so are technologies and techniques that pose particular problems to our defenses."
Clapper said he was especially concerned about a small number of al-Qaida fighters with experience fighting in Pakistan and Afghanistan, and who may be motivated to carry out strikes in the United States.