For 18 months, both prisons were without a governor.
An investigation is underway as to how a loophole in the law could have seen prisoners detained in both midlands prisons being released on a technicality.
For a period of 18 months, the Portlaoise and Midlands Prisons were left without a governor because of an administrative error during the appointment.
The issue meant then campus chief Ethel Gavin was statutorily unable to detain prisoners as she was not appointed as governor of the individual facilities.
Reporter with the Irish Examiner, Mick Clifford, says it could have been a costly error: