Department spokesman Ian Kelly told reporters that the U.S. released the five to the Iraqi government because it was obliged to do so under a U.S.-Iraqi security agreement that took effect several months ago. Whether they are now set free is up to the Iraqis.
He described the five Iranians as being "associated with" the Quds force, an element of the Iranian Revolutionary Guard Corps. U.S. officials believe the five were involved in training Iraqi militant groups.
Kelly said the possibility of the five creating further security problems in Iraq was "a big concern." And he said U.S. officials have communicated that concern to Baghdad.