The body of murdered American woman Sarai Sierra was returned to New York via a Turkish Airlines flight without charge on Thursday, according to local media report.

Turkish officials have closed off the area where her body was found.

Authorities concluded that 33-year-old Sierra was killed with a blow to the head. She had been in regular contact with her family on Staten Island during her three-week trip, which included a preplanned excursion to Amsterdam and a stop in Munich before she returned to Istanbul.

She disappeared on Jan. 21, and her body was found 12 days later near the remnants of the city's ancient walls. She was still wearing her jewelry, but her iPhone and iPad were missing.

Turkish police and the U.S. Federal Bureau of Investigation ( FBI) are investigating her death. Prosecutors on Monday got a court order to take blood and DNA samples from 21 people questioned in the death. More than 200 people have testified in the case.