Jack Letts, dubbed "Jihadi Jack", travelled to Syria in 2014 and was later captured by the Kurdish-led YPG, the group fighting against IS, when he left IS territory, the officials told the BBC.
Letts was captured in May.
A statement given to the BBC from the Democratic Federation of Northern Syria (DFNS), a self-declared autonomous region, said Letts had been taken to a prison in Qamishli, Rojava, northern Syria.
It said the case was still under investigation by the local police force of the DFNS, the Asayish.
Letts converted to Islam while at Cherwell comprehensive school in Oxford.
He travelled to Jordan, aged 18, in 2014. By later that year he was in IS-controlled territory in Syria. Letts married in Iraq and now has a child.
His parents have denied he went to Syria to fight with IS, and started a petition that claimed he had "disappeared in a Guantanamo-style black site" in Kurdish-controlled territory.
But Sinam Mohamad, the European representative of DFNS, strongly disputed this.
She told the BBC that its judicial bodies respected international human rights law and were treating Letts in accordance with the Geneva Convention and international human rights standards.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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