Washington: The US Federal Bureau of Investigation (FBI) has seen children as young as 15 being recruited by the Islamic State (IS) terrorist group, a media report said on Wednesday.
FBI's counter-terrorist division head Michael Steinbach is leading the effort to stay on top of the evolving threat landscape, which includes targeting and recruiting teenage Americans, CNN reported.
Steinbach said he "can't speak with 100 percent certainty that individuals of that age group have not gotten over there successfully".
It was extremely difficult to track every American who might travel abroad to join terrorist groups like the IS, Steinbach said.
He said that US law enforcement and intelligence agencies did not track individuals leaving the US for vacations in Europe.
"Once you get to Europe, you can easily get down to Turkey and into Syria," Steinbach added.
There is growing concern about homegrown violent extremism in the aftermath of last month's terror attacks in Paris.
Those strikes underscored the threat posed to the West by small groups of terrorists with Western passports who are influenced by the rhetoric espoused by the IS.
Steinbach is concerned that such type of attack could happen on US soil.
Steinbach said the FBI was working round the clock to combat the recruitment of Americans but US law enforcement could not do the job alone. It was up to families to speak up as well, he said.