India-born Sabrina de Sousa tells The Associated Press that US officials were in contact with authorities in both Portugal and Italy ahead of her release.
Officials in the United States, Italy and Portugal were not immediately available for comment.
De Sousa walked free yesterday, a day after Italy dropped its extradition request for her.
An Italian court had convicted her of taking part in the kidnapping of a Muslim cleric in Milan 14 years ago as part of the US "extraordinary rendition" anti-terrorism program.