Three American girls' plan to run away abroad were thwarted in Germany, and now the FBI says its investigating the possibility that they were trying to join the Islamic State in Syria, Fox News reported on Tuesday.

The girls were tracked down in Frankfurt, but are home now in Colorado, according to a law enforcement agent. They're all expected to dodge charges because they're minors under the age of 18. The girls are of Somali and Sudanese decent.

A law enforcement source said the girls were leaving the United States to join the ISIS military group. The official added that the girls may have been radicalized by a "slick media campaign" and sought to fulfill the messages peddled in the campaign. 

Someone close to the girls, who are aged 15 and 16, notified authorities of their possible intentions. It is believed the girls were in touch with someone in Germany who persuaded them to leave their homes.

Once in Germany, they were sent on a flight back to the United States, but may not be arrested or charged with anything because of their ages.

There have been other cases of high school age kids trying fly to Syria that haven't been made public, ABC News reported.  

"FBI Denver Division is aware of the situation and assisted with bringing the individuals back to Denver. The juveniles are safe and reunited with their families," FBI Denver spokeswoman Sue Payne said, according to ABC News.

One of the arguably most notable cases of teens becoming involved with ISIS involves Austrian girls Samra Kesinovic, 16, and her friend Sabina Selimovic, 15. They are said to be living in an ISIS - controlled city in Syria and may be pregnant, but have been able to get in touch with their families to tell them they want to come home. This may be difficult, officials have said, because they are known seen as the "poster girls" of the terrorist organization.