The two British jihadists arrested in Syria – part of the group nicknamed "The Beatles" – were trying to escape to Turkey, the Syrian Democratic Forces (SDF) have confirmed.
Kino Gabriel, a spokesman for the coalition fighters, told Sky News an investigation was now under way and that his colleagues were trying to get more information from Alexanda Kotey and El Shafee Elsheikh.
He said a decision on whether the men would be tried in Syria or in the UK would be made once the SDF investigation had concluded.
"Both of them were trying to escape to Turkey during the time (of their arrest) – our anti-terrorist unit conducted their operation and managed to capture them," said Mr Gabriel.
"We have been investigating with them since then and we are trying to get more information regarding the crimes that have been committed by them and to be able to get any information about their victims.
"So far we have confirmed that they belong to The Beatles gang, that is famous with the torture of foreign nationals who have been captured by ISIS or Daesh.
"We cannot release any more information regarding their situation or regarding the information we got from them because the investigation is still ongoing and we would still wait till the investigation is over."
He added: "After everything is over we will take a mutual decision with SDF's international partners regarding their future and whether they are going to be tried here or whether they will be moved to England."
The Londoners were members of the group of four Britons who are believed to have tortured and beheaded dozens of people.
British aid workers Alan Henning and David Haines, and American journalists James Foley and Steven Sotloff, are thought to be among their suspected victims.
Mr Haines' widow has since told Sky News she wants the two detained men to reveal where his body is located.
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Dragana Prodanovic Haines said: "We need him back – David deserves to be buried properly, we deserve to have a place where we can go and take flowers and remember him.
"That's the only thing I hope, they kept at least a little bit of humanity, so they can tell us where the bodies are. We need closure."