An unidentified law enforcement official told ABC News there are concerns Heda Umarova, 23, may have been radicalized by Islamist violence and could pose a threat to Americans overseas.
Umarova was a friend of Dzokhar Tsarnaev, charged in the April 2013 bombing at the Boston Marathon, and his brother Tamerlan, who was killed in a shootout with police. She has a U.S. passport, ABC News added, and traveled from Boston to Chechnya in July to visit relatives but has not returned.
Her family told federal authorities she stayed in Chechnya to marry a man she met, ABC News said.
She is believed to have posted jihadist imagery online and her younger brothers, Adam, 20, and Junes, 18, are under suspicion for their online support of the Tsarnaev brothers, authorities said.
"No one is calling Heda a terrorist, but her travel has certainly garnered some attention. People are concerned that a 23-year-old is in Chechnya, a country she fled from, and now she is deciding to stay on her own," the law enforcement official said.
Notable deaths of 2014 [PHOTOS]