an embolization device for positioning in a blood vessel comprises an elongated wire body which in its unloaded condition has a predetermined shape and has an elongated shape with a substantially straight center line during its insertion through a catheter to a placement site in the blood vessel and after its release from the catheter assumes a complexly curved shape which depends on the predetermined shape and on the blood vessel impact on the wire body . in its predetermined shape the wire body has at least one section located between its front and back ends in which the center line has substantially no curvature or such a small curvature that along a length of at least 20 mm it follows a helix - free path . the front end section of the wire body is adapted to be frictionally locked to the vessel wall when discharged from the catheter , before said helix - free section has been discharged from the catheter . when the helix - free section is discharged it will bend sideways and seek towards the middle of the vessel lumen and continue towards the opposite vessel wall where it is frictionally locked . at continued pushing out many such vessel - crossing wire portions occur , which provides efficient occlusion of the vessel . one advantage of the embolization device is that it may be used to occlude blood vessel areas . accordingly , a method is described for occluding a blood vessel area using the wire body .