The Data Protection Commissioner (DPC) is investigating after personal files held by the HSE were "compromised".
The matter relates to the storage and retention of personal data contained in paper records held by the HSE at external storage facilities.
As reported by the Irish Examiner, breaches of security were notified to the DPC by the HSE in respect of two locations which were accessed by unauthorised third parties.
Video footage showing paper medical records at these locations was subsequently circulated online.
The HSE was informed of the DPC's decision to investigate the matter on Tuesday.
DPC chair Des Hogan said while the investigation was launched following the two breach notifications, the commissioners now wish to expand the scope of the probe and "look wider".
