U.S. counter-terrorism officials are attempting to track down a female friend of the accused Boston Marathon bomber after she traveled to Chechnya last year and is believed to have since posted "alarming" jihadi imagery online, officials told ABC News.
Officials are concerned that Heda Umarova, 23, may have been radicalized to Islamist violence -- allegedly just like her friend Dzhokhar Tsarnaev, charged in the April 15 bombings, and his brother Tamerlan, who was killed in a police shootout -- and could pose a threat to Americans overseas because her U.S. passport allows easy foreign travel.
Umarova left Boston with her family in July with a round-trip ticket to visit relatives in their native Chechnya, but she failed to return to Massachusetts with her parents at the end of August. Her family told federal authorities and ABC News she stayed behind to get married after she met a man there during Ramadan.
Her younger brothers, Adam, 20, and Junes, 18, were already under suspicion by some investigators because of their online support for the Tsarnaev brothers and social media postings that included tweets with Dzhokhar a day before the blasts. A photo of Junes Umarov and Dzhokhar Tsarnaev lighting fireworks appeared on one social networking site in January 2013, an ABC News investigation found.
"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 that she fled from... and now she is deciding to stay on her own," a ranking law enforcement source involved in the Boston Marathon investigation told ABC News. The source said that her decision to stay in Chechnya also raised eyebrows because, at least until she is married, she didn't seem to have any "obvious means" of support.
"We were already concerned about the social media exchanged with her brothers, who remain on the radar, especially the younger brother Junes, who was Dzhokhar's best friend," the source added.
And now, sources said, the FBI has been monitoring Heda Umarova's apparent Internet posts recently, which include depictions of Chechen jihadis brandishing weapons and a photo-shopped image of a U.S. passport in a carry-on bag bearing the black flag of jihad.
Heda and her brothers did not respond to multiple attempts by ABC News to reach them through their parents and social media to comment on the sources' allegations.
In a brief interview at his family's home last month, Heda's father Hamzat Umarov told ABC News that he spoke to the "FBI and CIA" about the photographs but refused to talk about whether he believes his daughter is becoming radicalized.
"What does it mean, pictures? Pictures can be anywhere. It doesn't mean anything, the pictures. We don't want to talk about it. We talk with the FBI, everybody. The FBI came, CIA, everybody's come,'' he said.
Umarova's trip back to the same country from which her parents fled as refugees a decade ago to seek political asylum in the U.S. brought federal agents back to her family's Chelsea home -- the same second-floor apartment that armed agents searched last April during the manhunt for the accused marathon bomber, several law enforcement officials told ABC News.
Heda Umarova has not been indicted for any offenses, sources said.
A spokesman for the Boston FBI field office declined to comment on Heda Umarova or any possible threat she may pose. "It is the FBI's policy not to confirm or deny whether or not an investigation is being conducted,'' said Special Agent Gregory Comcowich.