The discovery of medical files in a park and on streets in Co Donegal happened after a break-in at a medical records centre, the HSE said said.
The private file of an elderly woman was found in a Letterkenny park by a family out walking on 9 June.
A number of other letters and files were also found in separate incidents over a number of weeks.
The letters also included two lists of 33 patients which had been found by litter wardens in Letterkenny in both March and May of this year.
The HSE has said storage containers at St Conal's medical facility, close to Letterkenny University Hospital, was broken into.
A lock on the container was smashed open and an undisclosed number of files taken.
The files at this particular centre relate to the records of deceased patients as well as secondary notes on patients.
A spokesperson confirmed that steel cages have now been fitted to locks around the cages on the medical records storage containers.
"A thorough investigation was carried out following the most recent incident and as a result steel door cages have been ordered for all doors for the ground floor of St Conal's.
"All containers have been fitted with lock boxes to prevent a reoccurrence of the recent breach where the lock had been broken to gain access to one of the containers.
"The loss of patient files were not as a result of negligence but as a result of theft so there will be no sanctions on staff," they said a statement.