Teen girls from Denver arrested in Germany were trying to join ISIS, U.S. officials say

BERLIN -- Three teenage girls who set out from a Denver suburb apparently bound for Syria to join extremists fighting there are back home after their parents alerted authorities and the trio was stopped in Germany, U.S. officials said.

The teens -- two sisters of Somali descent and a friend whose family is Sudanese, according to a Denver community leader -- were detained when their flight landed in Frankfurt on Friday after the FBI flagged their passports. They were flown back to Denver on Sunday, officials said.

Parents of the girls called the FBI after becoming concerned the girls may have been traveling to Turkey.

The FBI, which is investigating why the girls left, is "aware of the situation and assisted with bringing the individuals back to Denver. That is all the information we can provide at this time," said agency spokeswoman Sue Payne in Denver.

The girls, believed to be between the ages of 15 and 17, are U.S. citizens thought to have become radicalized in their hometown, officials say.

It's not exactly clear how the girls planned their trip or how they were going to make their way to Syria, but officials say their ultimate plan was to try and join extremists fighting there.

The FBI has spoken to the teens and interviewed their families, and the agency said at this point they are not facing any charges.