The FBI is worried that Americans are becoming radicalized by al-Qaeda-linked militant groups while fighting in the Syrian civil war, the Associated Press reports.
Some estimates place the number of Americans involved in the conflict at a couple dozen.
Feds have already arrested at least three Americans this year for planning to fight the Syrian leadership with a radical Islamic organization, Jabhat al-Nusrah, the AP reported.
Some are concerned about a flashback to the 1980s when an Afghanistan conflict attracted foreign fighters.