Baghdad ? Five U.S. contractors have been detained in the investigation of the slaying of another American in Baghdad’s Green Zone, officials said Sunday, in what may become the first case of U.S. citizens facing Iraqi justice under a security agreement that took effect this year.

U.S. and Iraqi officials said the five have not been charged in the death of Jim Kitterman, 60, a construction company owner from Houston, whose body was found May 22 in his car in the Green Zone. He had been blindfolded, bound and stabbed.

Police spokesman Maj. Gen. Abdul-Karim Khalaf said the Americans were being held at an Iraqi police station inside the Green Zone “in connection with a joint U.S.-Iraqi investigation” into Kitterman’s death but gave no further details.