Apparatus for searching for and detecting defects on parts that are substantially inaccessible, being located behind a wall, the apparatus comprising a first endoscope for illumination in visible light and for observation, the first endoscope and pipes for feeding and spraying penetration test substances being housed together in a rod which can be passed through an orifice in the wall in order to examine a part, the apparatus further comprising a second endoscope independent of the first endoscope and the rod for illuminating in ultraviolet light and for observing the portion of the part that has been treated by the penetration test substances.