Two British extremists believed to have been members of Islamic State's brutal executions group dubbed "The Beatles" have reportedly been captured.
Alexanda Kotey and El Shafee Elsheikh are the last two members of the cell to remain at large.
An image grab taken from a video released by the Islamic State (IS) shows a masked militant holding a knife and gesturing as he speaks to the camera in a desert landscape before a beheading. The two men are among four members of the ISIS cell that captured, tortured and beheaded more than two dozen hostages including American journalists James Foley and Steven Sotloff, and American aid worker Peter Kassig.
The US official did not give any information on the condition of the two or what would happen to them.
The most notorious of the four was Mohammed Emwazi, known as "Jihadi John", an executioner of hostages made famous by Islamic State videos of beheadings.
The fourth member, Davis, was convicted of being a member of a terrorist organisation and jailed for seven-and-a-half years at a court in Silivri, Turkey, in May 2017. "Kotey has also acted as an ISIL recruiter and is responsible for recruiting several United Kingdom nationals to join the terrorist organization".
Officials quoted by United States media said the two men had been captured by members of the US-backed Syrian Democratic Forces (SDF), who are targeting remnants of IS.
US officials did not provide any other details of the capture, but said the USA government with its coalition partners on the disposition of detainees held by the SDF.
The UK Foreign Office, meanwhile, said it did not comment on individual cases or investigations. ISIL is another acronym for the Islamic State.
The New York Times said that the SDF caught the men in January and have made them available to the U.S. military personnel for questioning.
The families of the men were not aware of the capture until the story was reported by news organisations, they told the BBC this evening.
In October, the group lost its "capital" of Raqqa to the SDF.
The SDF is an alliance of Kurdish and Arab fighters opposed to IS.
The US has said it aims to maintain an open-ended military presence in the country to ensure the jihadist group's defeat.