A top Italian anti-terrorism prosecutor says an ex-U.S. diplomat convicted of the CIA kidnapping of an Egyptian cleric has been detained in Portugal.

Armando Spataro told The Associated Press that Sabrina De Sousa was arrested at Lisbon Airport Monday. She was released from custody on Wednesday but her passport was seized pending a court decision on whether to turn her over to Italy to serve her six-year sentence.

De Sousa was among 26 Americans convicted in absentia over the 2004 kidnapping. Italy never made a formal extradition request for most of them; Spataro said it is likely she was picked up on a European arrest warrant issued automatically after a conviction.

De Sousa was initially acquitted due to diplomatic immunity, but was found guilty by a higher court in 2014.