BERLIN (AP) — German prosecutors are investigating how a Moroccan man convicted of helping the Hamburg-based Sept. 11, 2001, suicide pilots was apparently paid some 7,000 euros (,960) before he was deported to his homeland last year.

Mounir el Motassadeq was deported in October, shortly before completing his 15-year sentence for membership in a terrorist organization and being an accessory to murder.

An investigation by Hamburg prosecutors centers on an apparent payment from his prison account, used in Germany to hold money earned by inmates. The money is generally transferred to inmates on their release, but el Motassadeq was on a list of terror suspects whose assets are frozen.

Prosecutors’ spokeswoman Nana Frombach said Thursday they are investigating a suspected violation of Germany’s foreign trade and payments act following a complaint by the country’s central bank.