The CBI has always been a mystery even for insiders. Look at it: three Additional Director General rank posts are currently vacant even though plenty of eligible candidates are available. Many aspiring senior IPS officers have been gauging the prospects but some of them were clearly indicated that the posts were reserved for two internal candidates currently serving as Joint Directors in the Bureau. In fact, this is not a new thing. Since the functioning of CBI requires expertise and experience, ADG posts were often given in the past to the serving Jt Directors after their ADG empanelment. It may be noted that the CBI has one sanctioned post of Special Director (ADG rank) and three sanctioned posts of ADG. Usually, one ADG post is redesignated as Special Director as its creation is the prerogative and powers of CBI Director. CBI had rarely all three ADG posts functional. Often one ADG post remains dormant. Following the appointment of Y C Modi as NIA chief, all three ADG posts are currently vacant but the doors appear to be closed to outsiders.