In the field of airport baggage inspection, a multi-level screening procedure is used. When a first level screening system (18) detects a "suspicious region" inside a bag, it is transferred to a next level system (2) where the bag gets rescanned. According to the present invention, a device/method is provided for finding and tracking the suspicious region inside the baggage which allows to reduce the area to be rescanned significantly. For this purpose, the image from the first level system together with the position of the suspicious region within the image is transferred from the first level system to the second level system. On arrival of the bag at the second level (21), a simple X-ray transmission image is measured using an additional source/detector system (6). The two images are then rigidly registered in order to exactly determine the suspicious region in the second level scanner system.