BERLIN (AP) – German authorities have arrested a Syrian man on allegations he supported the extremist Nusra Front in his homeland.

Federal prosecutors said Wednesday the 33-year-old, identified only as Abdul Sattar A. I., was fighting for a paramilitary group associated with the Free Syrian Army when in April 2014, he organized the capture of Islamic State fighter Saleh A.

They allege he handed the man over to the Nusra Front, with the goal of arranging a prisoner exchange to get Nusra captives released by the Islamic State. The prisoner swap failed because Saleh A. escaped.

Prosecutors say A.I. was arrested Tuesday and his home in the Karlsruhe area was searched.

Saleh A. was arrested in Germany in September 2016, and is currently on trial for Islamic State membership.