ATLANTA • An FBI translator who was investigating a key Islamic State in Iraq and Syria (ISIS) operative travelled to Syria in 2014 to marry him, CNN reported yesterday, citing unsealed court papers.

Daniela Greene, who was working with the FBI as a contract linguist, was assigned to investigate German citizen Denis Cuspert in January 2014. It was unclear when the 38-year-old began communicating with Cuspert, but in June she lied to the FBI that she was going to Germany to see her family. She later travelled to Syria from Turkey.

Although Greene had warned her new husband that he was under investigation, she changed her mind within weeks of arriving in Syria and decided to return to the US. It was unclear, however, how the US authorities discovered Greene's actions, but a warrant was secretly issued for her arrest five weeks after she left for Syria.

Greene later pleaded guilty to making false statements involving international terrorism and was sentenced to two years in prison.

Cuspert, a 41-year-old rapper turned ISIS recruiter, had appeared in propaganda videos, including one in which he was seen holding a freshly severed human head.

According to CNN, Greene is now working as a hostess in a hotel lounge and did not want to discuss her case for fear of endangering her family. Commenting on the case, the FBI said it had taken "several steps in a variety of areas to identify and reduce security vulnerabilities", but did not elaborate.